Exhibit (i)

1601 K Street Washington, DC 20006-1600 202.778.9000 Fax 202.778.9100 www.klng.com

December 28, 2006

Heritage Series Trust

880 Carillon Parkway

St. Petersburg, Florida 33716

Ladies and Gentlemen:

We have acted as counsel to Heritage Series Trust, a business trust formed under the laws of the Commonwealth of Massachusetts (the “Trust”), in connection with the filing with the Securities and Exchange Commission (“SEC”) of Post-Effective Amendment No. 40 to the Trust’s Registration Statement on Form N-1A (File Nos. 33-57986; 811-7470) (the “Post-Effective Amendment”), registering an indefinite number of: (1) Class A, B and C shares of beneficial interest of the Core Equity Fund, Diversified Growth Fund, International Equity Fund, Mid Cap Stock Fund and Small Cap Stock Fund; (2) Class R-3 and R-5 shares of beneficial interest of the Core Equity Fund, Diversified Growth Fund, Mid Cap Stock Fund and Small Cap Stock Fund; and (3) Class I shares of beneficial interest of the Core Equity Fund, Diversified Growth Fund, Mid Cap Stock Fund and Small Cap Stock Fund, each a series of the Trust (the “Shares”) under the Securities Act of 1933, as amended (the “1933 Act”).

You have requested our opinion as to the matters set forth below in connection with the filing of the Post-Effective Amendment. For purposes of rendering that opinion, we have examined the Post-Effective Amendment, the Trust’s Declaration of Trust, as amended and Amended and Restated Bylaws of the Trust, and the action of the Trust that provides for the issuance of the Shares, and we have made such other investigation as we have deemed appropriate. We have examined and relied upon certificates of public officials and, as to certain matters of fact that are material to our opinions; we have also relied on a certificate of an officer of the Trust. In rendering our opinion, we also have made the assumptions that are customary in opinion letters of this kind. We have not verified any of those assumptions.

Our opinion, as set forth herein, is based on the facts in existence and the laws in effect on the date hereof and is limited to the federal laws of the United States of America and the laws of the Commonwealth of Massachusetts that, in our experience, generally are applicable to the issuance of shares by entities such as the Trust. We express no opinion with respect to any other laws.

Based upon and subject to the foregoing, we are of the opinion that:

1. The Shares to be issued pursuant to the Post-Effective Amendment have been duly authorized for issuance by the Trust; and

BOSTONŸDALLASŸHARRISBURGŸLONDONŸLOS ANGELESŸMIAMIŸNEWARKŸNEW YORKŸPALO ALTOŸPITTSBURGHŸSAN FRANCISCOŸWASHINGTON

Heritage Series Trust

December 28, 2006

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2. When issued and paid for upon the terms provided in the Post-Effective Amendment, the Shares to be issued pursuant to the Post-Effective Amendment will be validly issued, fully paid, and nonassessable. In this regard, however, we note that the Trust is a Massachusetts business trust and, under certain circumstances, shareholders of a Massachusetts business trust could be held personally liable for the obligations of the Trust.

This opinion is rendered solely in connection with the filing of the Post-Effective Amendment and supersedes any previous opinions of this firm in connection with the issuance of Shares. We hereby consent to the filing of this opinion with the SEC in connection with the Post-Effective Amendment and to the reference to this firm in the statement of additional information that is being filed as part of the Post-Effective Amendment. In giving our consent we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the 1933 Act or the rules and regulations of the SEC thereunder.

Very truly yours,

/s/ Kirkpatrick & Lockhart Nicholson Graham LLP

Kirkpatrick & Lockhart Nicholson Graham LLP

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