BLACKROCK HIGH YIELD BOND PORTFOLIO

BLACKROCK HIGH YIELD BOND PORTFOLIO - Class K Shares

JANUARY 27, 2017

Summary Prospectus

BlackRock Funds II | Class K Shares

►	BlackRock High Yield Bond Portfolio
	Class K: BRHYX

Before you invest, you may want to review the Fund’s prospectus, which contains more information about the Fund and its risks. You can find the Fund’s prospectus (including amendments and supplements) and other information about the Fund, including the Fund’s statement of additional information and shareholder report, online at http://www.blackrock.com/prospectus. You can also get this information at no cost by calling (800) 537-4942 or by sending an e-mail request to prospectus.request@blackrock.com, or from your financial professional. The Fund’s prospectus and statement of additional information, both dated January 27, 2017, as amended and supplemented from time to time, are incorporated by reference into (legally made a part of) this Summary Prospectus.

This Summary Prospectus contains information you should know before investing, including information about risks. Please read it before you invest and keep it for future reference.

The Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this Summary Prospectus. Any representation to the contrary is a criminal offense.

Not FDIC Insured • May Lose Value • No Bank Guarantee

Summary Prospectus

Key Facts About BlackRock High Yield Bond Portfolio

Investment Objective

The investment objective of the BlackRock High Yield Bond Portfolio (the “High Yield Fund” or the “Fund”) is to seek to maximize total return, consistent with income generation and prudent investment management.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)		Class K Shares
Management Fee¹		0.41%
Distribution and/or Service (12b-1) Fees		None
Other Expenses		0.12%
Interest Expense	0.01%
Other Expenses of the Fund	0.11%
Acquired Fund Fees and Expenses²		0.01%
Total Annual Fund Operating Expenses²		0.54%
Fee Waivers and/or Expense Reimbursements^1,3		—
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements^1,3		0.54%

¹	As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 42, BlackRock Advisors, LLC (“BlackRock”) has contractually agreed to waive the management fee with respect to any portion of the Fund’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BlackRock or its affiliates that have a contractual management fee, through January 31, 2018. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested trustees of BlackRock Funds II (the “Trust”) or by a vote of a majority of the outstanding voting securities of the Fund.
²	The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Fund’s most recent Annual Report, which do not include Acquired Fund Fees and Expenses.
³	As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 42, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.58% of average daily net assets through January 31, 2018. The Fund may have to repay some of these waivers and/or reimbursements to BlackRock in the two years following such waivers and/or reimbursements. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested trustees of the Trust or by a vote of a majority of the outstanding voting securities of the Fund.

Example:

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year	3 Years	5 Years	10 Years
Class K Shares	$55	$173	$302	$677

Portfolio Turnover:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 90% of the average value of its portfolio.

Principal Investment Strategies of the Fund

The High Yield Fund invests primarily in non-investment grade bonds with maturities of ten years or less. The High Yield Fund normally invests at least 80% of its assets in high yield bonds. The high yield securities (commonly called “junk bonds”) acquired by the High Yield Fund will generally be in the lower rating categories of the major rating agencies (BB or lower by Standard & Poor’s or Fitch Ratings, Inc. or Ba or lower by Moody’s Investor Services) or will be determined by the High Yield Fund management team to be of similar quality. Split rated bonds will be considered to have the higher credit rating. The Fund may invest up to 30% of its assets in non-dollar denominated bonds of issuers located outside of the United States. The High Yield Fund’s investment in non-dollar denominated bonds may be on a currency hedged or unhedged basis. The Fund may also invest in convertible and preferred securities. Convertible debt securities will be counted toward the Fund’s 80% policy to the extent they have characteristics similar to the securities included within that policy.

To add additional diversification, the management team can invest in a wide range of securities including corporate bonds, mezzanine investments, collateralized bond obligations, bank loans and mortgage-backed and asset-backed securities. The High Yield Fund can also invest, to the extent consistent with its investment objective, in non-U.S. and emerging market securities and currencies. The High Yield Fund may invest in securities of any rating, and may invest up to 10% of its assets (measured at the time of investment) in distressed securities that are in default or the issuers of which are in bankruptcy.

The High Yield Fund may buy or sell options or futures on a security or an index of securities, or enter into credit default swaps and interest rate or foreign currency transactions, including swaps (collectively, commonly known as derivatives). The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. The High Yield Fund may seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as reverse repurchase agreements or dollar rolls).

The High Yield Fund may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies.

Principal Risks of Investing in the Fund

Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.

■	Bank Loan Risk — The market for bank loans may not be highly liquid and the Fund may have difficulty selling them. These investments expose the Fund to the credit risk of both the financial institution and the underlying borrower.
■	Collateralized Bond Obligation Risk — The pool of high yield securities underlying collateralized bond obligations is typically separated into groupings called tranches representing different degrees of credit quality. The higher quality tranches have greater degrees of protection and pay lower interest rates. The lower tranches, with greater risk, pay higher interest rates.
■	Convertible Securities Risk — The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock.
■	Debt Securities Risk — Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
	Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise. The Fund may be subject to a greater risk of rising interest rates due to the current period of historically low rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations

	in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management. To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
	Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make principal and interest payments when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on the issuer’s financial condition and on the terms of the securities.
	Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
	Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
■	Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
	Volatility Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
	Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation.
	Market and Liquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.
	Valuation Risk — Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.
	Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.
	Leverage Risk — Certain transactions in derivatives involve substantial leverage risk and may expose the Fund to potential losses that exceed the amount originally invested by the Fund.
	Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.
	Regulatory Risk — Derivative contracts, including, without limitation, swaps, currency forwards and non-deliverable forwards, are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (“Dodd Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, certain derivatives will become subject to margin requirements and swap dealers will be required to collect margin from the Fund with respect to such derivatives. Implementation of such regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of swaps and other derivatives may increase the costs to the Fund of trading in these instruments and, as a result, may affect returns to investors in the Fund. In December 2015, the Securities and Exchange Commission proposed a new rule to regulate the use of derivatives by registered investment companies, such as the Fund. If the rule goes into effect, it could limit the ability of the Fund to invest or remain invested in derivatives.

■	Distressed Securities Risk — Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale.
■	Dollar Rolls Risk — Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage.
■	Emerging Markets Risk — Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets.
■	Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:

■	The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.
■	Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.
■	The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.
■	The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries.
■	Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.
■	Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.
■	The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries. These events may spread to other countries in Europe. These events may affect the value and liquidity of certain of the Fund’s investments.

■	Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that may cause income and principal losses for the Fund.
■	Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.
■	Liquidity Risk — Liquidity risk exists when particular investments are difficult to purchase or sell. The Fund’s investments in illiquid securities may reduce the returns of the Fund because it may be difficult to sell the illiquid securities at an advantageous time or price. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to liquidity risk. Liquidity risk may be the result of, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active market. Liquid investments may become illiquid or less liquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid and relatively less liquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor

	redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.
■	Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
■	Mezzanine Securities Risk — Mezzanine securities carry the risk that the issuer will not be able to meet its obligations and that the equity securities purchased with the mezzanine investments may lose value.
■	Mortgage- and Asset-Backed Securities Risks — Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities.
■	Preferred Securities Risk — Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred stock of larger companies.
■	Repurchase Agreements and Purchase and Sale Contracts Risk — If the other party to a repurchase agreement or purchase and sale contract defaults on its obligation under the agreement, the Fund may suffer delays and incur costs or lose money in exercising its rights under the agreement. If the seller fails to repurchase the security in either situation and the market value of the security declines, the Fund may lose money.
■	Reverse Repurchase Agreements Risk — Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences to the Fund.

Performance Information

The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index. Effective September 1, 2015, the Board of Trustees approved the reclassification of BlackRock Shares of the Fund as Class K Shares. The returns for Class K Shares prior to September 1, 2015, the commencement of operations of Class K Shares, are based upon performance of the Fund’s BlackRock Shares. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. The table includes all applicable fees. If the Fund’s investment manager and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting http://www.blackrock.com/funds or can be obtained by phone at (800) 882-0052.

Class K Shares

ANNUAL TOTAL RETURNS

BlackRock High Yield Bond Portfolio
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 17.16% (quarter ended June 30, 2009) and the lowest return for a quarter was -20.79% (quarter ended December 31, 2008).

As of 12/31/16 Average Annual Total Returns	1 Year	5 Years	10 Years
BlackRock High Yield Bond Portfolio — Class K Shares
Return Before Taxes	14.02%	7.74%	7.28%
Return After Taxes on Distributions	11.02%	4.83%	4.25%
Return After Taxes on Distributions and Sale of Fund Shares	7.86%	4.72%	4.33%
Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index (Reflects no deduction for fees, expenses or taxes)	17.13%	7.36%	7.55%

After-tax returns are calculated using the historical highest individual Federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Investment Manager

The Fund’s investment manager is BlackRock Advisors, LLC (previously defined as “BlackRock”).

Portfolio Managers

Name	Portfolio Manager of the Fund Since	Title
James Keenan, CFA	2007	Managing Director of BlackRock, Inc.
Mitchell Garfin, CFA	2009	Managing Director of BlackRock, Inc.
David Delbos	2014	Managing Director of BlackRock, Inc.
Derek Schoenhofen	2009	Director of BlackRock, Inc.

Purchase and Sale of Fund Shares

Class K Shares of the Fund are available only to (i) employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs and SARSEPs) (“Employer-Sponsored Retirement Plans”), (ii) collective trust funds, investment companies and other pooled investment vehicles, each of which may purchase shares of the Fund through a Financial Intermediary (as defined below) that has entered into an agreement with the Fund’s distributor to purchase such shares, (iii) “Institutional Investors,” which include, but are not limited to, endowments, foundations, family offices, local, city, and state governmental institutions, corporations and insurance company separate accounts, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares and (iv) any other investors who met the eligibility criteria for BlackRock Shares or

Class K Shares prior to August 15, 2016 and have continually held Class K Shares of the Fund in the same account since August 15, 2016.

You may purchase or redeem shares of the Fund each day the New York Stock Exchange is open. Purchase orders may also be placed by calling (800) 537-4942, by mail (c/o BlackRock, P.O. Box 9819, Providence, Rhode Island 02940-8019), or online at www.blackrock.com. Institutional Investors are subject to a $5 million minimum initial investment requirement. Other investors, including Employer-Sponsored Retirement Plans, have no minimum initial investment requirement. There is no minimum investment amount for additional purchases.

Tax Information

Different income tax rules apply depending on whether you are invested through a qualified plan exempt from tax under section 401(a) of the Internal Revenue Code of 1986, as amended. If you are invested through such a plan (and Fund shares are not “debt-financed property” to the plan), then the dividends paid by the Fund and the gain realized from a redemption or exchange of Fund shares will generally not be subject to Federal income taxes until you withdraw or receive distributions from the plan. If you are not invested through such a plan, then the Fund’s dividends and gain from a redemption or exchange may be subject to Federal income taxes and may be taxed as ordinary income or capital gains, unless you are a tax-exempt investor.

Payments to Broker/Dealers and Other Financial Intermediaries

If you purchase shares of the Fund through a financial professional or selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock, The PNC Financial Services Group, Inc. and their respective affiliates) (each a “Financial Intermediary”), the Fund and BlackRock Investments, LLC, the Fund’s distributor, or its affiliates may pay the Financial Intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the Financial Intermediary and your individual financial professional to recommend the Fund over another investment. Ask your individual financial professional or visit your Financial Intermediary’s website for more information.

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INVESTMENT COMPANY ACT FILE # 811-22061

BlackRock High Yield Bond Portfolio — Class K

SPRO-HYB-K-0117