His approach to directing is guided by his belief that character and relationships, along with an emphasis on genuine emotion over intellectualization, are the keys to unlocking the dramatic potential of a performance, a play, or a screenplay.
Walter Kerr praised Seidelman's 1970 revival of Clifford Odets' Awake and Sing as an "astonishingly fresh and deeply moving evening" and wrote also that it was "directed and played as nakedly as though no one were watching.
Seidelman also directed The Caller, a science fiction thriller shot at Rome’s Cinecittà Studios, starring Malcolm McDowell and Madolyn Smith and the 2007 film Black Friday (also known as The Kidnapping).
He also directed Walking Across Egypt with Ellen Burstyn, Echoes, a reincarnation thriller, and Puerto Vallarta Squeeze, starring Scott Glenn and Harvey Keitel in a film adaptation by Richard Alfieri of the novel by Robert James Waller.
Seidelman also directed Black Friday (also known as The Kidnapping) with Judd Nelson, and Sin of Innocence starring Dee Wallace and, in his film debut, Dermot Mulroney.
Seidelman's NBC movie Kate's Secret, starring Meredith Baxter Birney as a woman fighting bulimia, remains one of the most watched made-for-television films in TV history.
He hosted the PBS series Actors on Acting and staged Norman Lear’s 1982 all-star American Broadcasting Company variety show special I Love Liberty featuring Barbra Streisand, Jane Fonda, Burt Lancaster, Walter Matthau, Mary Tyler Moore, and Martin Sheen.
For regional theatres, he has directed Cat on a Hot Tin Roof, The Little Foxes, A Man for All Seasons, The Roar of the Greasepaint – The Smell of the Crowd, Romeo and Juliet, Stop the World – I Want to Get Off, and The Tempest, among others.
He has directed Richard Alfieri's Six Dance Lessons in Six Weeks in its Los Angeles premiere (with Uta Hagen and David Hyde Pierce) at the Geffen Playhouse[7] and on Broadway (with Polly Bergen and Mark Hamill),[6] in the West End (with Claire Bloom and Billy Zane),[8] at the Coconut Grove Playhouse (with Rue McClanahan and Mark Hamill),[9] and a Los Angeles revival (with Constance Towers and Jason Graae).
While researching the film Children of Rage, he lived extensively in the Middle East, including in refugee camps in Lebanon, where at one point, he was taken hostage by members of the Popular Front for the Liberation of Palestine.