Houston sent guards Kevin Martin and rookie Jeremy Lamb, two first-round picks and a second-round pick. The Thunder also sent center Cole Aldrich, Daequan Cook and Lazar Hayward.
Harden, who the Thunder drafted in 2009 with the third overall pick, is scheduled to be a free agent next summer, and was seeking a long-term maximum deal. Unless the sides could come to an agreement by Oct. 31, Harden would become a restricted free agent.
Oklahoma City was reluctant to pay Harden a maximum deal, believing they could not afford to go over the salary cap, and with the league's new cap penalties looming.
Out of Arizona State, Harden reportedly turned down a four-year deal for $52 million, according to Yahoo! Sports.
The Rockets will pair Harden with their big free agent splash, point guard Jeremy Lin. Houston, like many teams last season, made several moves to clear space and shore up draft picks to make a run at center Dwight Howard. Those attempts fell flat, and Houston continued their search for a star.
Harden averaged career highs in points and assists last season, with 16.8 and 3.7 respectively, and also hit 39 percent of his 3-pointers.
Adding the smooth shooting Martin, will lessen the scoring loss of Harden for Oklahoma City. The eight-year veteran has struggled with injuries, but has also averaged more than 20 points per game in six seasons.