Supplement dated September 10, 2020

to the Statement of Additional Information (the “SAI”), dated May 1, 2020, as supplemented, for the following funds:

Fund

Columbia Acorn Trust

 Columbia Acorn European Fund^SM

 Columbia Acorn International Select^SM

Effective immediately, the SAI is hereby supplemented to reflect that, as of July 31, 2020, the ownership of Stephen Kusmierczak, Co-President of Columbia Acorn Trust (the “Trust”), Co-Portfolio Manager of Columbia Acorn International Select and Portfolio Manager of Columbia Acorn European Fund, in the Trust's series is as follows: 

Portfolio Manager	Fund	Dollar Range of Equity Securities in the Fund Beneficially Owned
Stephen Kusmierczak	Columbia Acorn Fund	$500,001 - $1,000,000
	Columbia Acorn International	over $1 million
	Columbia Acorn European Fund	over $1 million
	Columbia Thermostat Fund	$1 - $10,000
	Columbia Acorn International Select	over $1 million

The rest of the section remains the same.

Shareholders should retain this Supplement for future reference.

SUP900_00_018_(09/20)