Born in Mount Vernon, New York, Kagan received his B.A. from Harvard University in 1967. He went on to attend the newly formed New York University Graduate Institute of Film & Television and was in the first class at the AFI Conservatory.

He has also been a prolific television Director, starting already in 1972 at the age of 26, directing The Most Crucial Game (starring Peter Falk, Robert Culp, Valerie Harper, Val Avery, Susan Howard, Dean Stockwell among others), an episode in the second Columbo season. In 1996, Kagan won an Primetime Emmy Award for Outstanding Directing for a Drama Series for the Chicago Hope episode "Leave of Absence". Other credits include the television movie Katherine: The Making of an American Revolutionary, which he also wrote, and Conspiracy: The Trial of the Chicago 8 for which he won the CableACE Award for Best Dramatic Special. Kagan also directed Roswell: The UFO Conspiracy, which garnered a Golden Globe Award nomination.

Kagan's feature film credits include the box-office hit Heroes (1977), The Big Fix (1978) a political comedy-thriller starring Richard Dreyfuss; The Chosen (1981), from the classic book of the same name by Chaim Potok; The Journey of Natty Gann (1985), the first American movie ever to win the Gold Prize at the Moscow International Film Festival; the underground comedy Big Man on Campus (1989); the cult classic fencing film By The Sword (1991); and the Hybrid film Golda's Balcony (2006), from the hit play of the same name.

Other television films include The Ballad of Lucy Whipple, Courage with Sophia Loren, Scott Joplin, Descending Angel for HBO and for Showtime Color of Justice, Bobbie's Girl, and Crown Heights, about the riots in 1991 which won the Humanitas Award in 2004 for "affirming the dignity of every person." This film also received an NAACP Image Award and the Directors Guild nomination for best family film. Kagan also directed a movie episode of Steven Spielberg's Emmy winning Taken. He has worked on several other series shows including The West Wing, The Guardian, Resurrection Blvd., Picket Fences, Boomtown and more.

He has served as artistic Director at the Robert Redford's Sundance Institute and is on a National Board Member of the Directors Guild of America and chairperson of its Special Projects Committee which provides cultural and educational programs for the 14,000 members. In 2004 he was honored with the Robert Aldrich Award for "extraordinary Service to the guild."

Kagan is also the author of the book Directors Close Up (Scarecrow, 2006). 0240804066