Sullivan began his career at ABC in 1976 and by the early 80s, after a stint as director of current drama, was named director of comedy development. He left the network in 1983 to become a producer under contract to Warner Bros. TV, where he nurtured and helped develop the comedy "Growing Pains", created by Neal Marlens and featuring Alan Thicke and Joanna Kerns as the parents of three kids. Sullivan was executive producer of the show for its first five seasons (1985-90), during which he also developed and executive produced the spin-off "Just the 10 of Us" (ABC, 1988-1990) which focused on a high school coach and his growing family. In 1993, he formed Michael Sullivan Productions, an independent firm, which he abandoned in 1994 to join UPN. After his tenure at the fledgling network ended in 1997, he returned to the ranks of independent producers.
Sullivan also has served as vice-chair of Paulist Communications, a nonprofit organization which has arms that include the Human Family Institute--which awards the Humanitas Prizes--and a production entity. Among the projects of the latter with which Sullivan has had some involvement was the feature biopic "Romero" (1989).