DFA INVESTMENT DIMENSIONS GROUP INC.

INSTITUTIONAL CLASS SHARES

CLASS R1 SHARES

CLASS R2 SHARES

U.S. Small Cap Value Portfolio U.S. Targeted Value Portfolio U.S. Core Equity 1 Portfolio U.S. Core Equity 2 Portfolio U.S. Vector Equity Portfolio U.S. Small Cap Portfolio U.S. Micro Cap Portfolio International Core Equity Portfolio Japanese Small Company Portfolio Asia Pacific Small Company Portfolio United Kingdom Small Company Portfolio Continental Small Company Portfolio DFA International Small Cap Value Portfolio International Vector Equity Portfolio World ex U.S. Targeted Value Portfolio World ex U.S. Core Equity Portfolio Emerging Markets Portfolio Emerging Markets Value Portfolio Emerging Markets Targeted Value Portfolio Emerging Markets Small Cap Portfolio Emerging Markets Core Equity Portfolio U.S. Small Cap Growth Portfolio International Small Cap Growth Portfolio U.S. Social Core Equity 2 Portfolio U.S. Sustainability Core 1 Portfolio International Sustainability Core 1 Portfolio International Social Core Equity Portfolio Emerging Markets Sustainability Core 1 Portfolio Emerging Markets Social Core Equity Portfolio Tax-Managed U.S. Marketwide Value Portfolio Tax-Managed U.S. Targeted Value Portfolio Tax-Managed U.S. Equity Portfolio Tax-Managed U.S. Small Cap Portfolio T.A. U.S. Core Equity 2 Portfolio T.A. World ex U.S. Core Equity Portfolio VA U.S. Targeted Value Portfolio VA International Small Portfolio

DIMENSIONAL INVESTMENT GROUP INC.

Tax-Managed U.S. Marketwide Value Portfolio II

Emerging Markets Portfolio II

SUPPLEMENT TO THE PROSPECTUSES DATED FEBRUARY 28, 2019

The purpose of this Supplement is to incorporate the changes discussed below into the Prospectuses dated February 28, 2019, as supplemented, of the portfolios listed above, each a series of DFA Investment Dimensions Group Inc. or Dimensional Investment Group Inc.  Accordingly, the Prospectuses are revised as follows:

(1) For U.S. Small Cap Value Portfolio, U.S. Targeted Value Portfolio (Institutional Class), U.S. Core Equity 1 Portfolio, U.S. Core Equity 2 Portfolio, U.S. Vector Equity Portfolio, U.S. Small Cap Portfolio, and U.S. Micro Cap Portfolio, the following paragraph is added to the “ADDITIONAL INFORMATION ON INVESTMENT OBJECTIVES AND POLICIES—PORTFOLIO TRANSACTIONS—ALL PORTFOLIOS” section of the Prospectus:

For each Portfolio that invests in companies that the Advisor considers to be small capitalization, the Advisor may consider a small capitalization company’s investment characteristics with respect to other eligible companies when making investment decisions and may exclude a small capitalization company when the Advisor determines it to be appropriate. In assessing a company’s investment characteristics, the Advisor may consider ratios such as recent changes in assets or book value scaled by current assets or book value. Under normal circumstances, each Portfolio will seek to limit such exclusion to no more than 5% of the eligible small capitalization company universe in each country that the Portfolio invests.

(2) For U.S. Targeted Value Portfolio (Class R1 and Class R2), International Core Equity Portfolio, Japanese Small Company Portfolio, Asia Pacific Small Company Portfolio, United Kingdom

Small Company Portfolio, Continental Small Company Portfolio, DFA International Small Cap Value Portfolio, International Vector Equity Portfolio, World ex U.S. Targeted Value Portfolio, World ex U.S. Core Equity Portfolio, Emerging Markets Value Portfolio (Institutional Class and Class R2), Emerging Markets Targeted Value Portfolio, Emerging Markets Small Cap Portfolio, and Emerging Markets Core Equity Portfolio, the following paragraph is added to the “ADDITIONAL INFORMATION ON INVESTMENT OBJECTIVES AND POLICIES—PORTFOLIO TRANSACTIONS—ALL PORTFOLIOS” sections of the respective Prospectuses:

For each Portfolio or Master Fund that invests in companies that the Advisor considers to be small capitalization, the Advisor may consider a small capitalization company’s investment characteristics with respect to other eligible companies when making investment decisions and may exclude a small capitalization company when the Advisor determines it to be appropriate. In assessing a company’s investment characteristics, the Advisor may consider ratios such as recent changes in assets or book value scaled by current assets or book value. Under normal circumstances, each Portfolio or Master Fund will seek to limit such exclusion to no more than 5% of the eligible small capitalization company universe in each country that the Portfolio or Master Fund invests.

(3) For U.S. Small Cap Growth Portfolio and International Small Cap Growth Portfolio, the following paragraph is added to the “ADDITIONAL INFORMATION ON OBJECTIVES AND POLICIES— PORTFOLIO TRANSACTIONS” section of the Prospectus:

For each Portfolio that invests in companies that the Advisor considers to be small capitalization, the Advisor may consider a small capitalization company’s investment characteristics with respect to other eligible companies when making investment decisions and may exclude a small capitalization company when the Advisor determines it to be appropriate. In assessing a company’s investment characteristics, the Advisor may consider ratios such as recent changes in assets or book value scaled by current assets or book value. Under normal circumstances, each Portfolio will seek to limit such exclusion to no more than 5% of the eligible small capitalization company universe in each country that the Portfolio invests.

(4) For U.S. Social Core Equity 2 Portfolio, U.S. Sustainability Core 1 Portfolio, International Sustainability Core 1 Portfolio, International Social Core Equity Portfolio, Emerging Markets Sustainability Core 1 Portfolio, and Emerging Markets Social Core Equity Portfolio, the following paragraph is added to the “ADDITIONAL INFORMATION ON OBJECTIVES AND POLICIES—PORTFOLIO TRANSACTIONS—EQUITY PORTFOLIOS” section of the Prospectus:

For each Portfolio that invests in companies that the Advisor considers to be small capitalization, the Advisor may consider a small capitalization company’s investment characteristics with respect to other eligible companies when making investment decisions and may exclude a small capitalization company when the Advisor determines it to be appropriate. In assessing a company’s investment characteristics, the Advisor may consider ratios such as recent changes in assets or book value scaled by current assets or book value. Under normal circumstances, each Portfolio will seek to limit such exclusion to no more than 5% of the eligible small capitalization company universe in each country that the Portfolio invests.

(5) For Tax-Managed U.S. Marketwide Value Portfolio, Tax-Managed U.S. Targeted Value Portfolio, Tax-Managed U.S. Equity Portfolio, Tax-Managed U.S. Small Cap Portfolio, T.A. U.S. Core Equity 2 Portfolio, T.A. World ex U.S. Core Equity Portfolio, and Tax-Managed U.S. Marketwide Value Portfolio II, the following paragraph is added to the “ADDITIONAL INFORMATION ON OBJECTIVES AND POLICIES—PORTFOLIO TRANSACTIONS” section of the respective Prospectuses:

For each Portfolio or Master Fund that invests in companies that the Advisor considers to be small capitalization, the Advisor may consider a small capitalization company’s investment

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characteristics with respect to other eligible companies when making investment decisions and may exclude a small capitalization company when the Advisor determines it to be appropriate. In assessing a company’s investment characteristics, the Advisor may consider ratios such as recent changes in assets or book value scaled by current assets or book value. Under normal circumstances, each Portfolio or Master Fund will seek to limit such exclusion to no more than 5% of the eligible small capitalization company universe in each country that the Portfolio or Master Fund invests.

(6) For VA U.S. Targeted Value Portfolio and VA International Small Portfolio, the following paragraph is added to the “ADDITIONAL INFORMATION ON OBJECTIVES AND POLICIES— PORTFOLIO TRANSACTIONS—DOMESTIC AND INTERNATIONAL EQUITY PORTFOLIOS” section of the Prospectus:

For each Portfolio that invests in companies that the Advisor considers to be small capitalization, the Advisor may consider a small capitalization company’s investment characteristics with respect to other eligible companies when making investment decisions and may exclude a small capitalization company when the Advisor determines it to be appropriate. In assessing a company’s investment characteristics, the Advisor may consider ratios such as recent changes in assets or book value scaled by current assets or book value. Under normal circumstances, each Portfolio will seek to limit such exclusion to no more than 5% of the eligible small capitalization company universe in each country that the Portfolio invests.

(7) For Emerging Markets Portfolio, Emerging Markets Targeted Value Portfolio, Emerging Markets Value Portfolio, Emerging Markets Small Cap Portfolio, and Emerging Markets Portfolio II, Mitchell J. Firestein no longer serves as a portfolio manager to each Portfolio. Accordingly, all references to Mitchell J. Firestein are hereby removed from the respective Prospectuses.

The date of this Supplement is July 8, 2019

SUPP070819

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DFA INVESTMENT DIMENSIONS GROUP INC.

INSTITUTIONAL CLASS SHARES

CLASS R2 SHARES

Emerging Markets Portfolio

Emerging Markets Targeted Value Portfolio

 Emerging Markets Value Portfolio

Emerging Markets Small Cap Portfolio

DIMENSIONAL INVESTMENT GROUP INC.

Emerging Markets Portfolio II

SUPPLEMENT TO THE STATEMENTS OF ADDITIONAL INFORMATION DATED FEBRUARY 28, 2019

For Emerging Markets Portfolio, Emerging Markets Targeted Value Portfolio, Emerging Markets Value Portfolio (Institutional Class and Class R2), Emerging Markets Small Cap Portfolio, and Emerging Markets Portfolio II, Mitchell J. Firestein no longer serves as a portfolio manager to each Portfolio. Accordingly, all references to Mitchell J. Firestein are hereby removed from the respective statements of additional information.

The date of this Supplement is July 8, 2019