As filed with the Securities and Exchange Commission on May 6, 2013

File Nos. 333-138560

811-21978

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933	x
Pre-Effective Amendment No.	¨
Post-Effective Amendment No. 21	x
and/or
REGISTRATION STATEMENT
UNDER
THE INVESTMENT COMPANY ACT OF 1940	x
Amendment No. 22	x

(Check appropriate box or boxes)

PIONEER SERIES TRUST VI*

(Exact Name of Registrant as Specified in Charter)

60 State Street, Boston, Massachusetts 02109

(Address of Principal Executive Offices) (Zip Code)

Registrant’s Telephone Number, including Area Code: (617) 742-7825

Terrence J. Cullen, Pioneer Investment Management, Inc.,

60 State Street, Boston, Massachusetts 02109

(Name and Address of Agent for Service)

It is proposed that this filing will become effective (check appropriate box):

x immediately upon filing pursuant to paragraph (b)

¨ on [date] pursuant to paragraph (b)

¨ 60 days after filing pursuant to paragraph (a)(1)

¨ on [date] pursuant to paragraph (a)(1)

¨ 75 days after filing pursuant to paragraph (a)(2)

¨ on [date] pursuant to paragraph (a)(2) of Rule 485

If appropriate, check the following box:

¨ This post-effective amendment designates a new effective date for a Previously filed post-effective amendment.

* This filing relates to Pioneer Multi-Asset Real Return Fund, a series of the Registrant.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Trust certifies that it meets all of the requirements for effectiveness of this Registration Statement under Rule 485(b) under the Securities Act of 1933, and has duly caused this Post-Effective Admendment No. 21 to its Registration Statement to be signed on its behalf by the undersigned, duly authorized, in the City of Boston and The Commonwealth of Massachusetts, on the 6th day of May, 2013.

PIONEER SERIES TRUST VI
By:	/s/ Daniel K. Kingsbury
	Daniel K. Kingsbury
	Executive Vice President

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities indicated below on May 6, 2013:

	Signature	Title
	John F. Cogan, Jr.*	President (Principal
	John F. Cogan, Jr.	Executive Officer) and
		Trustee
	Mark E. Bradley*	Treasurer (Principal Financial and
	Mark E. Bradley	Accounting Officer)
	David R. Bock*	Trustee
	David R. Bock
	Benjamin M. Friedman*	Trustee
	Benjamin M. Friedman
	Margaret B. W. Graham*	Trustee
	Margaret B. W. Graham
	/s/ Daniel K. Kingsbury	Executive Vice President
	Daniel K. Kingsbury	and Trustee
	Thomas J. Perna*	Chairman of the Board
	Thomas J. Perna	and Trustee
	Marguerite A. Piret*	Trustee
	Marguerite A. Piret
	Stephen K. West*	Trustee
	Stephen K. West
*By:	/s/ Daniel K. Kingsbury	Dated: May 6, 2013
	Daniel K. Kingsbury

Attorney-in-Fact

Pioneer Cayman Commodity Fund Ltd. certifies that it has duly caused this Registration Statement of Pioneer Series Trust VI, with respect only to information that specifically relates to Pioneer Cayman Commodity Fund Ltd., to be signed on its behalf by the undersigned, duly authorized, in the city of Boston, and Commonwealth of Massachussetts, on the 6th day of May, 2013.

PIONEER CAYMAN COMMODITY FUND, LTD.
By:	/s/ Daniel K. Kingsbury
	Daniel K. Kingsbury
	Director

This Registration Statement of Pioneer Series Trust VI, with respect only to information that specifically relates to Pioneer Cayman Commodity Fund Ltd., has been signed below by the following person in the capacity indicated below on May 6, 2013.

SIGNATURE	TITLE
/s/ Daniel K. Kingsbury	Director
Daniel K. Kingsbury

EXHIBIT INDEX

Index Number	Description of Index
EX-101. INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Document
EX-101.DEF	XBRL Taxonomy Extension Definition Document
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase