"You know, I voted for him in 2008 and I plan to stick with him in 2012, and I'll be voting for he and Vice President Joe Biden next month," he said on CBS' "This Morning."
Asked whether it was an endorsement, he said, "Yes."
Powell praised the president's handling of the economy and ending of the Iraq War.
"I think we ought to keep on the track we are on," he said.
Powell said he had the "utmost respect" for Mitt Romney but criticized his tax plan.
He said Romney's foreign policy was a "moving target." "One day he has a certain strong view about staying in Afghanistan, but then on Monday night he agrees with the withdrawal. Same thing in Iraq. On every issue that was discussed on Monday night, Gov. Romney agreed with the president with some nuances. But this is quite a different set of foreign policy views than he had earlier in the campaign."
Powell, a Republican who served in President George W. Bush's first term, backed Obama in 2008. He was frequently mentioned as a potential Republican challenger against Bill Clinton in 1996, but decided against it.
POWELL: Not only am I uncomfortable with what Governor Romney is proposing for his economic plan, I have concerns about his views on foreign policy. The governor who was speaking on Monday night at the debate was saying things that were quite different from what he said earlier so I’m not quite sure which governor Romney we would be getting with respect to foreign policy.
O’DONNELL: What concerns do you have with governor Romney’s foreign policy?
POWELL: Well it’s hard to fix it, I mean it’s a moving target, one day he has a certain strong view about staying in Afghanistan but then on Monday night he agrees with the withdrawal, the same thing in Iraq and almost every issue that was discussed on Monday night, governor Romney agreed with the president with some nuances but this is quite a different set of foreign policy views than he had earlier in the campaign and my concern which I’ve expressed previously in a public way is that sometimes I don’t sense he has thought through these issues as thoroughly as he should have and he gets advice from his campaign staff that he then has to adjust or modify as they go along.
ROSE: Are you concerned about the people that are advising governor Romney?
POWELL: I think there are some very very strong neoconservative views that are presented by the governor that I have some trouble with.