- Betty White as Catherine Piper in Seasons 1-3, 5
- Scott Bakula as Jack Ross (4.13, “Glow in the Dark”)
- Ed Begley, Jr. as Clifford Cabot (2 episodes in Season 2, 1 episode in Season 3)
- Ralph Bellamy as Denny’s father (3.18, “Son of the Defender”) (footage from 1957 episode of Studio One)
- Shelley Berman as Judge Robert Sanders (3 episodes in Season 2, 6 episodes in Season 3, 2 episodes in Season 4)
- Jill Brennan as Gracie Jane (a parody of Nancy Grace) (2 episodes in Season 2, 7 episodes in Season 3, 4 episodes in Season 4)
- David Dean Bottrell as Lincoln Meyer (8 episodes in Season 3)
- Jayne Brook as Rachel Lewiston (5 episodes in Season 2)
- Delta Burke as Bella Horowitz (5 episodes in Season 3)
- Marisa Coughlan as Melissa Hughes (9 episodes in Season 2, 3 episodes in Season 3)
- William Daniels as Judge Milton Brody (1 episode in Season 5)
- Christine Ebersole as Sunny Fields (4.18 “Indecent Proposals”)
- Rupert Everett as Malcolm Holmes (2 episodes in Season 2)
- Frances Fisher as Carrie Lancing (1.02 “Still Crazy After All These Years”)
- Michael J. Fox as Daniel Post (5 episodes in Season 2, 1 episode in Season 3)
- Currie Graham as ADA Frank Ginsberg (3 episodes in Season 2, 3 episodes in Season 3, 1 episode in Season 4)
- Henry Gibson as Judge Clark Brown (3 episodes in Seasons 1, 2 and 3, 10 episodes in Season 4, 2 episodes in Season 5)
- Meredith Eaton-Gilden as Bethany Horowitz (14 episodes in Season 3, 1 episode in Season 4, 1 episode in Season 5)
- Mary Gross as Leigh Swift (3 episodes in Season 4)
- John Michael Higgins as Jerry Austin (2 episodes in Season 1)
- Alison La Placa as Andrea Michele (2 episodes in Season 4)
- Heather Locklear as Kelly Nolan (2 episodes in Season 2)
- Nia Long as Vanessa Walker (3 episodes in Season 3)
- Shelley Long as Miriam Watson (1.17, “Death Be Not Proud”)
- Jane Lynch as Joanna Monroe (3 episodes in Season 3, 1 episode in Season 5)
- Larry Miller as Edwin Poole (2 episodes in Season 1, 1 episode in Season 2, 1 episode in Season 5)
- Megan Mullally as Renata Hill (3.17, The Bride Wore Blood)
- Gail O’Grady as Judge Gloria Weldon (4 episodes in Season 3, 3 episodes in Season 4)
- Meredith Patterson as Missy Tiggs (2 episodes in Season 2, 1 episode in Season 3, 1 episode in Season 4)
- Ethan Phillips as Michael Schiller (3 episodes in Season 3)
- Parker Posey as Marlene Stanger (3 episodes in Season 2, 1 episode in Season 3)
- Freddie Prinze, Jr. as Donny Crane (2 episodes in Season 1, 1 episode in Season 2)
- Missi Pyle as Renee Winger (2 episodes in Season 3, 1 episode in Season 4)
- Carl Reiner as Milton Bombay (Episode 1.16, Let Sales Ring)
- Christopher Rich as Melvin Palmer (1 episode in Season 2, 1 episode in Season 3, 2 episodes in Season 4, 2 episodes in Season 5)
- Jeri Ryan as Courtney Reese (2 hour finale of Season 2)
- Katey Sagal as Barbara Little (5 episodes in Season 3)
- Tom Selleck as Ivan Tiggs (3 episodes in Season 2, 1 episode in Season 3)
- Al Sharpton as Himself (2 episodes in Season 1)
- Armin Shimerman as Judge Brian Hooper (7 episodes in Season 3)
- Robert Wagner as Barry Goal (2 hour finale of Season 2)
- Kerry Washington as Chelina Hall (4 episodes in Season 1, 1 episode in Season 2)
- Jaleel White as Kevin Givens (1 episode in Season 3)
- Melora Hardin as Sharon Brant (1st episode in Season 1)
- Elizabeth Mitchell as Christine Pauley (2 episodes in Season 1)
Many actors in the series were Star Trek alumni: William Shatner, John Larroquette, René Auberjonois, Henry Gibson, Scott Bakula, Ron Canada, Elizabeth Dennehy, Patrick Fabian, Gary Anthony Williams (video game), Mark L. Taylor, Colby French, Steven Culp, Pamela Adlon, Ivar Brogger, Thomas F. Wilson, Lamont Thompson, Gregg Daniel, Miriam Flynn, Mark Moses, Paul Dooley, Dan Gilvezan, Tony Todd, April Grace, Michael Bofshever, Jim Jansen, Billy Mayo, Stephen Lee, Lawrence Pressman, Michael G. Hagerty, Michael Ensign, Ron Ostrow, Ed Begley Jr., Christopher Neiman, Matthew Kaminsky, Zach Grenier, Ann Cusack, Dakin Matthews, Mark Chait, Michelle Forbes, Clyde Kusatsu, Annie Wersching, Ellen Bry, Armin Shimmerman, Ethan Phillips, Jeri Ryan, Dennis Cockrum, Robert Foxworth, David Burke, Ray Proscia, Don McManus, Lorna Raver, Jennifer Parsons, Ken Land, Andrew Prine, Matt Malloy, Daniel Roebuck, Fran Bennett, Joanna Cassidy, Corbin Bernsen,
and Patti Yasutake.
Several actors in the series were also Seinfeld alumni: James Spader, Candace Bergen, Constance Zimmer, Michelle Forbes, Armin Shimmerman, Robert Wagner, Larry Miller, Richard Fancy, Brenda Strong, Debra Mooney, Wayne Wilderson, Michael G. Hagerty, Stephen Tobolowsky, Kevin Dunn, Veanne Cox, Megan Mullally, and Corbin Bernsen.
