Sean O'Hair est né le 11 juillet 1982 au Texas, États-Unis. Il est marié avec Jaclyn Lucas depuis décembre 2002. Lui et Jaclyn Lucas ont trois enfants.
His father made him sign two contract at age 17 and at 19 that called for Sean to pay him 10% of his earnings for life; in 2005, Marc O'Hair announced that he had released Sean from the contracts.