497

The interactive data file included as an exhibit to this filing relates to the supplement to the prospectuses for Columbia Acorn Fund, Columbia Acorn International, Columbia Acorn USA, Columbia Acorn International Select, Columbia Acorn Select, Columbia Thermostat Fund, Columbia Acorn Emerging Markets Fund and Columbia Acorn European Fund filed pursuant to Rule 497(e) under the Securities Act of 1933, as amended, on November 1, 2017 (Accession No. 0001193125-17-328436), which is incorporated herein by reference.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Dec. 31, 2016
Registrant Name	dei_EntityRegistrantName	COLUMBIA ACORN TRUST
Central Index Key	dei_EntityCentralIndexKey	0000002110
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Nov. 01, 2017
Document Effective Date	dei_DocumentEffectiveDate	Nov. 01, 2017
Prospectus Date	rr_ProspectusDate	May 01, 2017

XML

May 01, 2017

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Acorn^® Fund

Columbia Acorn International^®

Columbia Acorn USA^®

Columbia Acorn International Select^SM

Columbia Acorn Select^SM

Columbia Thermostat Fund^SM

Columbia Acorn Emerging Markets Fund^SM

Columbia Acorn European Fund^SM

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:                                                                              

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

COLUMBIA ACORN TRUST

Prospectus Date

rr_ProspectusDate

May 01, 2017

Supplement [Text Block]

cat_SupplementTextBlock

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Acorn^® Fund

Columbia Acorn International^®

Columbia Acorn USA^®

Columbia Acorn International Select^SM

Columbia Acorn Select^SM

Columbia Thermostat Fund^SM

Columbia Acorn Emerging Markets Fund^SM

Columbia Acorn European Fund^SM

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:                                                                              

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

Columbia Acorn Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

cat_SupplementTextBlock

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Acorn^® Fund

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

Columbia Acorn International

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

cat_SupplementTextBlock

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Acorn International^®

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

Columbia Acorn USA

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

cat_SupplementTextBlock

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Acorn USA^®

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

Columbia Acorn International Select

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

cat_SupplementTextBlock

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Acorn International Select^SM

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

Columbia Acorn Select

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

cat_SupplementTextBlock

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Acorn Select^SM

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

Columbia Thermostat Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

cat_SupplementTextBlock

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Thermostat Fund^SM

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

Columbia Acorn Emerging Markets Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

cat_SupplementTextBlock

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Acorn Emerging Markets Fund^SM

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

Columbia Acorn European Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

cat_SupplementTextBlock

Supplement dated November 1, 2017

to the Prospectuses and Statement of Additional Information (SAI) dated May 1, 2017,

as supplemented, for the following Funds:

Funds

COLUMBIA ACORN TRUST

Columbia Acorn European Fund^SM

Effective immediately, each Fund’s Prospectus and SAI are supplemented as follows:

Class R4, Class R5, Class Y and Class Z shares are renamed and all references to such share classes are hereby replaced with the following new share class names:

Former Share Class Name	New Share Class Name (and abbreviation)
(prior to November 1, 2017)	(as of November 1, 2017)
Class R4	Advisor Class (Class Adv)
Class R5	Institutional 2 Class (Class Inst2)
Class Y	Institutional 3 Class (Class Inst3)
Class Z	Institutional Class (Class Inst)

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	COLUMBIA ACORN TRUST
Prospectus Date	rr_ProspectusDate	May 01, 2017
Document Creation Date	dei_DocumentCreationDate	Nov. 01, 2017