Sean Patrick Hayes was born and raised in the Chicago suburb of Glen Ellyn, Illinois. His father, Ronald, a lithographer, left the family when Sean was a young child. His mother, Mary, works at a food bank, and raised Sean and his four siblings on her own. Sean supported himself as a classical pianist and as a member of a pop band for five years, while attending Illinois State University, where he majored in performance and orchestral conducting. He began his post-collegiate professional career in Chicago theatre, as musical director at the Pheasant Run Theater for several years, appearing on stage in several productions as well. He also appeared in the original production of "Role Play" at the Organic Theatre.