SECOND AMENDMENT TO CONTRIBUTION AGREEMENT

Exhibit 2.5

SECOND AMENDMENT TO

CONTRIBUTION AGREEMENT

This SECOND AMENDMENT TO CONTRIBUTION AGREEMENT (this “ Amendment ”) is entered into as of January 16, 2007 by and among ONEOK, Inc., an Oklahoma corporation (“ ONEOK ”), ONEOK Partners, L.P., a Delaware limited partnership, formerly known as Northern Border Partners, L.P., (“ ONEOK Partners “), and ONEOK Partners Intermediate Limited Partnership (the “ ILP ”, and together with ONEOK Partners, the “ Partnerships ”) (each a “ Party ” and together, the “ Parties ”). Each capitalized term used herein but not defined shall have the meaning given such term in of the Contribution Agreement (as defined below).

W I T N E S S E T H

WHEREAS , the Parties previously entered into that certain Contribution Agreement dated as of February 14, 2006, as amended by that certain First Amendment to Contribution Agreement dated as of April 6, 2006 (collectively, the “ Contribution Agreement ”) and now desire to further amend the Cont