"Senator Obama is uniquely positioned to unite our nation and move beyond the divisiveness and partisan skirmishes that too often characterize politics as usual in Washington," he said in a statement released by the Obama campaign.
"Senator Obama and his positive message reflect the best of America," Henry added.
Oklahomans chose Hillary Clinton over Obama in the state's Feb. 5th primary by a significant margin, 55 percent to 31 percent.
Henry had previously said he wouldn't back a candidate until the Democratic National Convention in late August. Three Oklahoma superdelegates now back Obama, while one backs Clinton and six remain uncommitted.