Report of Independent Registered Public Accounting Firm

To the Shareholders and Board of Trustees of
Pioneer Mid Cap Value Fund:

In planning and performing our audit of the financial statements of
Pioneer Mid Cap Value Fund (the "Fund") as of and for the year ended
October 31, 2019, in accordance with the standards of the Public
Company Accounting Oversight Board (United States), we considered the
Fund's internal control over financial reporting, including controls over
safeguarding securities, as a basis for designing our auditing
procedures for the purpose of expressing our opinion on the financial
statements and to comply with the requirements of Form N-CEN, but not for
the purpose of expressing an opinion on the effectiveness of the Fund's
internal control over financial reporting.  Accordingly, we express no
such opinion.

The management of the Fund is responsible for establishing and maintaining
effective internal control over financial reporting. In fulfilling this
responsibility, estimates and judgments by management are required to assess
the expected benefits and related costs of controls. A company's internal
control over financial reporting is a process designed to provide reasonable
assurance regarding the reliability of financial reporting and the
preparation of financial statements for external purposes in accordance with
U.S. generally accepted accounting principles. A company's internal control
over financial reporting includes those policies and procedures that (1)
pertain to the maintenance of records that, in reasonable detail, accurately
and fairly reflect the transactions and dispositions of the assets of the
company; (2) provide reasonable assurance that transactions are recorded as
necessary to permit preparation of financial statements in accordance with
U.S. generally accepted accounting principles, and that receipts and
expenditures of the company are being made only in accordance with
authorizations of management and directors of the company; and (3) provide
reasonable assurance regarding prevention or timely detection
of unauthorized acquisition, use or disposition of a company's assets that
could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting
may not prevent or detect misstatements. Also, projections of any evaluation
of effectiveness to future periods are subject to the risk that controls may
become inadequate because of changes in conditions, or that the degree of
compliance with the policies or procedures may deteriorate.

A deficiency in internal control over financial reporting exists when the
design or operation of a control does not allow management or employees,
in the normal course of performing their assigned functions, to prevent
or detect misstatements on a timely basis. A material weakness is a
deficiency, or a combination of deficiencies, in internal control over
financial reporting, such that there is a reasonable possibility that a
material misstatement of the company's annual or interim financial
statements will not be prevented or detected on a timely basis.

Our consideration of the Fund's internal control over financial reporting
was for the limited purpose described in the first paragraph and would not
necessarily disclose all deficiencies in internal control that might be
material weaknesses under standards established by the Public Company
Accounting Oversight Board (United States). However, we noted no
deficiencies in the Fund's internal control over financial
reporting and its operation, including controls over safeguarding
securities that we consider to be a material weakness as defined
above as of October 31, 2019.

This report is intended solely for the information and use of
management and the Board of Trustees of Pioneer Mid Cap Value Fund,
and the Securities and Exchange Commission and is not intended to be and
should not be used by anyone other than these specified parties.


/s/ ERNST& YOUNG LLP


Boston, Massachusetts
December 20, 2019