CERTIFICATIONS
                                 --------------


I, John F. Cogan, Jr., certify that:

1. I have reviewed this report on Form N-CSR of Pioneer Short Term
Income Fund;

2. Based on my knowledge, this report does not contain any untrue
statement of a material fact or omit to state a material fact
necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect
to the period covered by this report;

3. Based on my knowledge, the financial statements, and other
financial information included in this report, fairly present in all
material respects the financial condition, results of operations,
changes in net assets, and cash flows (if the financial statements are
required to include a statement of cash flows) of the registrant as of,
and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as
defined in Rule 30a-3(c) under the Investment Company Act of
1940) and internal control over financial reporting (as defined in
Rule 30a-3(d) under the Investment Company Act of 1940) for the
registrant and have:

   a) Designed such disclosure controls and procedures, or caused
such disclosure controls and procedures to be designed under our
supervision, to ensure that material information relating to the
registrant, including its consolidated subsidiaries, is made known to
us by others within those entities, particularly during the period in
which this report is being prepared;
   b) Designed such internal control over financial reporting, or
caused such internal control over financial reporting to be designed
under our supervision, to provide reasonable assurance regarding the
reliability of financial reporting and the preparation of financial
statements for external in accordance with generally accepted
accounting principles;
   c) Evaluated the effectiveness of the registrant's disclosure controls
and procedures and presented in this report our conclusions about the
effectiveness of the disclosure controls and procedures, as of a date
within 90 days prior to the filing date of this report based on such
evaluation; and
   d) Disclosed in this report any change in the registrant's internal
control over financial reporting that occurred during the second
fiscal quarter of the period covered by this report that has materially
affected, or is reasonably likely to materially affect, the registrant's
internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed to the
registrant's auditors and the audit committee of the registrant's board
of directors (or persons performing the equivalent functions):

 a) All significant deficiencies in the design or operation of internal
controls over financial reporting which are reasonably likely to
adversely affect the registrant's ability to record, process, summarize,
and report financial information; and
 b) Any fraud, whether or not material, that involves management or
other employees who have a significant role in the registrant's
internal control over financial reporting.



Date:  October 30, 2012  		         /s/ John F. Cogan, Jr.
                                                  John F. Cogan, Jr.
                                                  President


<PAGE>


                                 CERTIFICATIONS
                                 --------------


I, Mark Bradley, certify that:

1. I have reviewed this report on Form N-CSR of Pioneer Short Term
Income Fund;

2. Based on my knowledge, this report does not contain any untrue
statement of a material fact or omit to state a material fact
necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect
to the period covered by this report;

3. Based on my knowledge, the financial statements, and other
financial information included in this report, fairly present in all
material respects the financial condition, results of operations,
changes in net assets, and cash flows (if the financial statements are
required to include a statement of cash flows) of the registrant as of,
and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as
defined in Rule 30a-3(c) under the Investment Company Act of
1940) and internal control over financial reporting (as defined in
Rule 30a-3(d) under the Investment Company Act of 1940) for the
registrant and have:

      a) Designed such disclosure controls and procedures, or caused
such disclosure controls and procedures to be designed under our
supervision, to ensure that material information relating to the
registrant, including its consolidated subsidiaries, is made known to
us by others within those entities, particularly during the period in
which this report is being prepared;
   b) Designed such internal control over financial reporting, or
caused such internal control over financial reporting to be designed
under our supervision, to provide reasonable assurance regarding the
reliability of financial reporting and the preparation of financial
statements for external in accordance with generally accepted
accounting principles;
   c) Evaluated the effectiveness of the registrant's disclosure controls
and procedures and presented in this report our conclusions about the
effectiveness of the disclosure controls and procedures, as of a date
within 90 days prior to the filing date of this report based on such
evaluation; and
   d) Disclosed in this report any change in the registrant's internal
control over financial reporting that occurred during the second
fiscal quarter of the period covered by this report that has materially
affected, or is reasonably likely to materially affect, the registrant's
internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed to the
registrant's auditors and the audit committee of the registrant's board
of directors (or persons performing the equivalent functions):

 a) All significant deficiencies in the design or operation of internal
controls over financial reporting which are reasonably likely to
adversely affect the registrant's ability to record, process, summarize,
and report financial information; and
 b) Any fraud, whether or not material, that involves management or
other employees who have a significant role in the registrant's
internal control over financial reporting.


Date:  October 30, 2012     	       		  /s/ Mark Bradley
                                                  Mark Bradley
                         		Treasurer & Chief Accounting
					& Financial Officer


<PAGE>


                            SECTION 906 CERTIFICATION


Pursuant to 18 U.S.C. ss. 1350, the undersigned officer of Pioneer
Short Term Income Fund (the "Fund"), hereby certifies, to the best of
his knowledge, that the Fund's Report on Form N-CSR for the period
ended August 31, 2012 (the "Report") fully complies with the requirements
of Section 13 (a) or 15 (d), as applicable, of the Securities Exchange Act
of 1934 and that the information contained in the Report fairly presents,
in all material respects, the financial condition and results of
operations of the Fund.


Dated: October 30, 2012



/s/ John F. Cogan, Jr.
John F. Cogan, Jr.
President


This certification is being furnished solely pursuant to 18 U.S.C. ss. 1350
and is not being filed as part of the Report or a separate disclosure document.

A signed original of this written statement required by section 906 has been
provided to the Fund and will be retained by the Fund and furnished to the SEC
or its staff upon request.

<PAGE>


                            SECTION 906 CERTIFICATION


Pursuant to 18 U.S.C. ss. 1350, the undersigned officer of Pioneer
Short Term Income Fund (the "Fund"), hereby certifies, to the best of
his knowledge, that the Fund's Report on Form N-CSR for the period
ended August 31, 2012 (the "Report") fully complies with the requirements
of Section 13 (a) or 15 (d), as applicable, of the Securities Exchange Act
of 1934 and that the information contained in the Report fairly presents,
in all material respects, the financial condition and results of
operations of the Fund.


Dated: October 30, 2012



/s/ Mark Bradley
Mark Bradley
Treasurer & Chief Accounting & Financial Officer


This certification is being furnished solely pursuant to 18 U.S.C. ss. 1350 and
is not being filed as part of the Report or a separate disclosure document.

A signed original of this written statement required by section 906 has been
provided to the Fund and will be retained by the Fund and furnished to the SEC
or its staff upon request.