Blagojevich made the revelation to Diane Sawyer on "Good Morning America" on the day his impeachment trial is set to begin. That trial is expected to toss him out of office.
The governor said that Winfrey's name came up as a potential successor to Obama in the Senate.
Watch Gov. Blagojevich's Interview With ABC News' Cynthia McFadden On "Nightline" Tonight at 11:35 p.m. ET
"She seemed to be someone who had helped Barack Obama in a significant way to become president," Blagojevich said. Blagojevich added that "she had a much broader bully pulpit than a lot of senators."
His consideration of Winfrey was tempered, he suggested, by the fact that "she probably wouldn't take it, and then if you offered it to her, how would you do it in a way it wasn't a gimmick to embarrass her."
Later on "The View," he added that Winfrey was appealing because she was "an African-American woman who probably by herself has more influence than 100 senators."
One of his hesitations, he said, was "Would she take the call of the governor of Illinois because Oprah is Oprah and I'm only the governor of Illinois."
Blagojevich said his consideration of Winfrey was "interrupted on Dec. 9," the day he was arrested by the FBI.
Winfrey, who endorsed Obama's presidential bid and showcased his candidacy on her show, said she missed "GMA" this morning because she slept late.
"If I had been watching from the treadmill where I'm usually watching, I would have fallen off the treadmill," Winfrey told her friend Gayle King during the Sirius XM radio show "Oprah and Friends."
Winfrey said she was "pretty amused" by Blagojevich's revelation.
"I think I could be a senator, but I'm not interested," Winfrey said.
Blagojevich's appearance on "GMA" was part of the governor's media blitz on the day that his impeachment trial is to begin in Springfield, Ill. -- without him. Blagojevich has already conceded that he will probably be convicted of corruption charges, but is refusing to resign or to attend the trial to defend himself.
Instead, he is scheduled to appear on "GMA," ABC's "The View," the "Today" show and "Larry King Live."
The governor insisted he was innocent but was boycotting his trial because he was not allowed to introduce witnesses like Obama's chief of staff Rahm Emanuel and the president's top adviser Valerie Jarrett.
"I'm talking to Americans to let them know what's happening in the land of Lincoln," Blagojevich said.
When asked whether he had tried to auction off Obama's Senate seat, Blagojevich said, "Absolutely not and I'll have a chance in a criminal case to show my innocence and bring witnesses."
Reminded that many people, including Obama, have called on him to resign and that Mayor Richard Daley even called him "cuckoo," the governor said, "Here's a question I have to you, to Mayor Daley and everyone else: Whatever happened to the presumption of innocence?"
"The fix is in," Blagojevich told "GMA." "They want me out of the way" so the Illinois legislature can enact a large tax increase, he said.
Illinois state Sen. Matt Murphy scoffed at the governor's argument.
"First let's work through all that red herring he just served us all for breakfast," Murphy told "GMA."
He called Blagojevich's argument that the trial was unfair the "most self-serving ludicrous statement I've ever heard in my life."
A conviction would make Blagojevich the first governor in Illinois history to be removed from office.
During his "GMA" appearance, he also defended his wife, who has been compared to Lady McBeth after surveillance tapes reportedly caught her encouraging her husband's allegedly illegal activities.
"My wife is a loving wife who cares for our children. She's the best person I know, a person of great character and integrity," Blagojevich said.
He said he tells his children, Amy, 10, and Annie, 4, "the most important part is they should know their father is not the person they're trying to say he is."
Compares Himself to King and Ghandi The governor has been waging a bizarre defense since his arrest by FBI agents on Dec. 9. He has complained that the trial is rigged and compared himself to a cowboy being lynched, as well as to such martyrs to justice as Martin Luther King and Mahatma Ghandi.
The most spectacular of the accusations against Blagojevich is that he tried to sell the Senate seat vacated by Obama to the highest bidder.
In a remarkable demonstration of his political shrewdness, Blagojevich forced the U.S. Senate to accept his appointment of Roland Burris to that seat after the Senate's leaders said they would never accept anyone named by the tainted governor.