Born in Waterville, Maine, he attended Princeton University and Boston University School of Law and initially worked as a lawyer in Boston. Only in the 1980s he became involved with screenwriting; initially, he wrote several episodes for the L.A. Law, which he later produced as well, and later created the Picket Fences, Chicago Hope, The Practice, Ally McBeal, and Boston Public series.
Kelley married actress Michelle Pfeiffer in 1993. They have two children, a girl adopted by Pfeiffer before the marriage and a son.