File Number: 33-34801
                                                Filed Pursuant to Rule 497(e) of
                                                      the Securities Act of 1933


                                                              September 28, 2018


                           PIONEER MID CAP VALUE FUND


                SUPPLEMENT TO THE PROSPECTUS DATED MARCH 1, 2018


FUND SUMMARY
Effective September 28, 2018, the following replaces the corresponding
information under the heading "Management" in the section entitled "Fund
summary":


MANAGEMENT


                    
INVESTMENT ADVISER     Amundi Pioneer Asset Management, Inc.
PORTFOLIO MANAGEMENT   Edward T. Shadek Jr., Senior Vice President and
                       Director of Mid Cap Value, U.S. of Amundi
                       Pioneer (lead portfolio manager of the fund
                       since 2013); Raymond Haddad, Vice President
                       of Amundi Pioneer (portfolio manager of the
                       fund since March 2018); and Timothy P.
                       Stanish, Vice President of Amundi Pioneer
                       (portfolio manager of the fund since September
                       2018)



MANAGEMENT
Effective September 28, 2018, the following replaces the corresponding
information under the heading "Portfolio management" in the section entitled
"Management":

Day-to-day management of the fund is the responsibility of Edward T. Shadek
Jr., Senior Vice President and Director of Mid Cap Value, U.S. of Amundi
Pioneer (lead portfolio manager of the fund since 2013), Raymond Haddad, Vice
President of Amundi Pioneer (portfolio manager of the fund since March 2018),
and Timothy P. Stanish, Vice President of Amundi Pioneer (portfolio manager of
the fund since September 2018). The domestic equity team supports Mr. Shadek,
Mr. Haddad and Mr. Stanish. Members of this team manage other Pioneer funds
investing primarily in U.S. equity securities. The portfolio managers and the
team also may draw upon the research and investment management expertise of the
global research teams, which provide fundamental and quantitative research on
companies and include members from one or more of Amundi Pioneer's affiliates.
Mr. Shadek


joined Amundi Pioneer in 2012. Prior to joining Amundi Pioneer, he was
co-founder and portfolio manager at Shaylor Capital. From 1997 to 2009, Mr.
Shadek was Senior Managing Director and Deputy Head of Investments at Putnam
Investments. Mr. Haddad joined Amundi Pioneer in 2014. Prior to joining Amundi
Pioneer, he was a General Partner at Cedrus Capital Management from 2011 to
2014. Mr. Stanish joined Amundi Pioneer in 2018. Prior to joining Amundi
Pioneer, he was at EVA Dimensions LLC, where he served as Managing Director and
Global Head of Fundamental Research from 2015 to 2018 and as a Senior Equity
Analyst from 2012 to 2015.



























                                                                   31283-00-0918
                                (Copyright)2018 Amundi Pioneer Distributor, Inc.
                                             Underwriter of Pioneer mutual funds
                                                                     Member SIPC


                                                              September 28, 2018


                           PIONEER MID CAP VALUE FUND


            SUPPLEMENT TO THE SUMMARY PROSPECTUS DATED MARCH 1, 2018


FUND SUMMARY
Effective September 28, 2018, the following replaces the corresponding
information under the heading "Management" in the section entitled "Fund
summary":


MANAGEMENT


                    
INVESTMENT ADVISER     Amundi Pioneer Asset Management, Inc.
PORTFOLIO MANAGEMENT   Edward T. Shadek Jr., Senior Vice President and
                       Director of Mid Cap Value, U.S. of Amundi
                       Pioneer (lead portfolio manager of the fund
                       since 2013); Raymond Haddad, Vice President
                       of Amundi Pioneer (portfolio manager of the
                       fund since March 2018); and Timothy P.
                       Stanish, Vice President of Amundi Pioneer
                       (portfolio manager of the fund since September
                       2018)



                                                                   31285-00-0918
                                (Copyright)2018 Amundi Pioneer Distributor, Inc.
                                             Underwriter of Pioneer mutual funds
                                                                     Member SIPC