BINGHAM MCCUTCHEN LLP
                                    ONE FEDERAL STREET
                               BOSTON, MASSACHUSETTS 02110

                                                               September 5, 2014



Pioneer Ibbotson Asset Allocation Series
60 State Street
Boston, Massachusetts  02109

Ladies and Gentlemen:

       We have acted as counsel to Pioneer Ibbotson Asset Allocation Series, a
Delaware statutory trust, in its individual capacity (the "Trust") and on behalf
of its series Pioneer Ibbotson Growth Allocation Fund (the "Acquiring Fund"), in
connection with the Trust's Registration Statement on Form N-14 to be filed with
the Securities and Exchange Commission on or about September 5, 2014 (the
"Registration Statement"), with respect to the Acquiring Fund's Class A, Class C
and Class Y shares of beneficial interest (the "Shares") to be issued in
exchange for the assets of Pioneer Aggressive Allocation Fund (the "Target
Fund"), a series of the Trust, as described in the Registration Statement (the
"Reorganization"). You have requested that we deliver this opinion in connection
with the Trust's filing of the Registration Statement.

       In connection with the furnishing of this opinion, we have examined the
following documents:

              (a) A certificate of the Secretary of State of the State of
       Delaware, dated as of a recent date, as to the existence of the Trust;

              (b) A copy, certified by the Secretary of State of the State of
       Delaware, of the Trust's Certificate of Trust filed with the Secretary of
       State (the "Certificate of Trust");

              (c) A certificate executed by the Secretary of the Trust,
       certifying as to, and attaching copies of, the Trust's Agreement and
       Declaration of Trust (the "Declaration"), the Trust's By-Laws (the
       "By-Laws"), and the resolutions adopted by the Trustees of the Trust
       authorizing the Reorganization and the issuance of the Shares on behalf
       of the Acquiring Fund (the "Resolutions");

              (d) a printer's proof, received on September 5, 2014, of the
       Registration Statement; and



September 5, 2014
Page 2

              (e) a copy of the Agreement and Plan of Reorganization to be
       entered into by the Acquiring Fund and the Target Fund in the form
       included as Exhibit A to the Registration Statement referred to in
       paragraph (d) above (the "Agreement and Plan of Reorganization").

       In such examination, we have assumed the genuineness of all signatures,
the conformity to the originals of all of the documents reviewed by us as
copies, including conformed copies, the authenticity and completeness of all
original documents reviewed by us in original or copy form and the legal
competence of each individual executing any document. We have assumed for the
purposes of this opinion that (i) the Registration Statement as filed with the
Securities and Exchange Commission will be in substantially the form of the
printer's proof referred to in paragraph (d) above; (ii) the Agreement and Plan
of Reorganization will be duly completed, executed and delivered by the parties
thereto in substantially the form of the copy referred to in paragraph (e)
above; and (iii) that the Declaration, the By-Laws, the Certificate of Trust,
the Resolutions and the Agreement and Plan of Reorganization will not have been
amended, modified or withdrawn and will be in full force and effect on the date
of issuance of such Shares.

       This opinion is based entirely on our review of the documents listed
above and such other documents as we have deemed necessary or appropriate for
the purposes of this opinion and such investigation of law as we have deemed
necessary or appropriate. We have made no other review or investigation of any
kind whatsoever, and we have assumed, without independent inquiry, the accuracy
of the information set forth in such documents.

       This opinion is limited solely to the Delaware Statutory Trust Act (which
for this purpose includes applicable provisions of the Delaware Constitution and
reported judicial decisions interpreting these laws) to the extent that the same
may apply to or govern the transactions referred to herein, and we express no
opinion with respect to the laws of any other jurisdiction or to any other laws
of the State of Delaware. Further, we express no opinion as to any state or
federal securities laws, including the securities laws of the State of Delaware.
No opinion is given herein as to the choice of law or internal substantive rules
of law which any tribunal may apply to such transaction. In addition, to the
extent that the Declaration or the By-Laws refer to, incorporate or require
compliance with, the Investment Company Act of 1940, as amended, or any other
law or regulation applicable to the Trust, except for the Delaware Statutory
Trust Act, as aforesaid, we have assumed compliance by the Trust with such Act
and such other laws and regulations.

       We understand that all of the foregoing assumptions and limitations are
acceptable to you.


September 5, 2014
Page 3


       Based upon and subject to the foregoing, please be advised that it is our
opinion that the Shares, when issued and sold in accordance with the
Declaration, the By-Laws, and the Resolutions and for the consideration
described in the Agreement and Plan of Reorganization, will be validly issued,
fully paid and nonassessable.

       This opinion is given as of the date hereof and we assume no obligation
to update this opinion to reflect any changes in law or any other facts or
circumstances which may hereafter come to our attention. We hereby consent to
the filing of this opinion as an exhibit to the Registration Statement. In
rendering this opinion and giving this consent, we do not admit that we are in
the category of persons whose consent is required under Section 7 of the
Securities Act of 1933, as amended, or the rules and regulations of the
Securities and Exchange Commission thereunder.



                                           Very truly yours,


                                           BINGHAM McCUTCHEN LLP