Report of Independent Registered Public Accounting Firm

To the Shareholders and Board of Trustees of
Pioneer Series Trust XI

In planning and performing our audits of the financial statements of Pioneer
Core Equity Fund (the "Fund") (one of the funds constituting Pioneer Series
Trust XI),  as of and for the year ended December 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
December 31, 2019.

This report is intended solely for the information and use of management
and the Board of Trustees of Pioneer Series Trust XI, 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
February 26, 2020