O'Leary claimed to have a master's degree in education and to have played college football for three years, but checks into his background showed it wasn't true.
"Due to a selfish and thoughtless act many years ago, I have personally embarrassed Notre Dame, its alumni and fans," O'Leary said in a statement released Friday by the university.
A biography released by Notre Dame on Sunday when they announced his hiring said O'Leary received a master's degree from New York University in 1972. O'Leary was a student there but did not receive a degree, said John Beckman, assistant vice president for public affairs at NYU.
O'Leary, 55, also never earned a letter playing football at New Hampshire even though his biography says he earned three. In fact, the school said he never played in a game.
The sudden resignation was one of the most embarrassing blows to the storied Notre Dame football program, famous for Rockne, Leahy, the Four Horsemen and winning one "for the Gipper."
"The integrity and credibility of Notre Dame is impeccable and with that in mind, I will resign my position as head football coach," O'Leary's statement said. His resignation was effective Thursday.
Notre Dame athletic director Kevin White said O'Leary has acknowledged inaccuracies in his biographical materials, "including his academic background."
"I understand that these inaccuracies represent a very human failing; nonetheless, they constitute a breach of trust that makes it impossible for us to go forward with our relationship," White said.
The search for a new coach will begin immediately, White said.
Notre Dame quarterback Carlyle Holiday was stunned by the news.
"It's a big shock," he said in an interview with Sporting News radio on Friday. "I never knew anything could happen like this before. (We've) just got to keep going on and find a new coach in a hurry ... try to get things going."
O'Leary, who left Georgia Tech on Sunday to become coach of the Irish, is listed in his biography in the Georgia Tech media guide as a three-time letter-winner at New Hampshire at offensive line and fullback. It also was included in a biography handed out by Notre Dame after his hiring to replace Bob Davie was announced.
But O'Leary went to New Hampshire only for two years, and never made it into a game.
O'Leary transferred to New Hampshire after two years at the University of Dubuque in Iowa. He said he was on the New Hampshire team in 1967 and 1968, but was unable to play his first year because of mononucleosis, and did not play his second year because of a knee injury.
Casey Robin, an offensive guard for the Irish who completed his eligibility this fall, said he agreed with O'Leary's decision to resign.
"He was talking about loyalty and even honesty, and obviously he didn't live u to that expectation," Robin said. "The team needs some honesty and loyalty from a coach."
Officials with Georgia Tech's athletic department did not immediately return a call Friday seeking comment.
Though O'Leary has said he was not sure how the information got into his biography, a document obtained by The Union Leader of Manchester indicates he listed the information when hired as a coach at Syracuse in 1980.
According to the school's sports information department, coaches and athletes personally filled out the biographical forms. The newspaper reported Friday that O'Leary's documents list "Univ. of New Hampshire 3 yr. lettered" as part of his athletic background.
The sports information department at New Hampshire said it has no record of O'Leary on a football roster, and that it does not keep records of letter winners.
O'Leary is listed as a 1968 graduate of New Hampshire with a degree in physical education.
"I just am surprised and shocked that he had to resign because of something like this," current New Hampshire football coach Sean McDonnell said. "It's awful, awful sad. He's a tremendous football coach. I've followed his career with interest. From the times I've talked to him, I know him as a guy with great integrity."
O'Leary was 52-33 in seven seasons at Georgia Tech, helping it earn five straight bowl invitations for the first time since the 1950s.
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