787 Seventh Avenue New York, NY 10019-6099 Tel: 212 728 8000 Fax: 212 728 8111

March 22, 2013

VIA EDGAR

Securities and Exchange Commission

100 F Street, NE

Washington, DC 20549

Re: BlackRock GNMA Portfolio, a series of BlackRock Funds II

(File No. 333-142592 and File No. 811-22061)

Ladies and Gentlemen:

On behalf of BlackRock Funds II and pursuant to Rule 497(e) under the Securities Act of 1933, as amended, attached for filing are exhibits containing interactive data format risk/return summary information that mirrors the risk/return summary information in a supplement, dated March 19, 2013, to the Prospectus, dated January 28, 2013, for BlackRock GNMA Portfolio (the “Fund”). The purpose of the filing is to submit the 497(e) filing dated March 19, 2013 in XBRL for the Fund.

Any questions or comments on this filing should be directed to the undersigned at 212-728-8510.

Very truly yours,

/s/ Anthony Geron

Anthony Geron

Enclosures

cc: Ben Archibald, Esq., BlackRock Advisors, LLC