| An | Titlu | Rol | Note |
|---|
| 1968 | Crazy World, Crazy People | diverse personaje | special TV |
| 1970 | Dan August | Coley Smith | Episodul: "Quadrangle for Death" |
| 1971 | Hawaii Five-O | Ryan Moore / Mike Welles | 2 episoade |
| 1972–1976 | The Waltons | Rev. Matthew Fordwick | rol secundar (18 episoade) |
| 1973 | Medical Center | Ronnie | Episodul: "End of the Line" |
| Bachelor-at-Law | Ben Sykes | episod pilot nevândut |
| M*A*S*H | Pvt. Carter | Episodul: "Deal Me Out" |
| 1974 | Kojak | Kenny Soames | Episodul: "Deliver Us Some Evil" |
| Owen Marshall, Counselor at Law | Greg | Episodul: "To Keep and Bear Arms" |
| The Bob Newhart Show | Dave | Episodul: "Sorry, Wrong Mother" |
| 1975 | Movin' On | Casey | Episodul: "Landslide" |
| Rhoda | Vince Mazuma | Episodul: "Chest Pains" |
| Mannix | Cliff Elgin | Episodul: "Hardball" |
| Great Performances | Richard | Episodul: "Who's Happy Now?" |
| The Bob Crane Show | Hornbeck | Episodul: "Son of the Campus Capers" |
| Petrocelli | John Oleson | Episodul: "Chain of Command" |
| Barnaby Jones | Joe Rockwell | Episodul: "The Price of Terror" |
| The Streets of San Francisco | John 'Johnny' Steiner | Episodul: "Murder by Proxy" |
| The Night That Panicked America | Walter Wingate | film de televiziune |
| The Mary Tyler Moore Show | Reverend Chatfield | Episodul: "Ted's Wedding" |
| The Rookies | Hap Dawson | Episodul: "Reluctant Hero" |
| 1976 | Starsky & Hutch | Tom Cole | Episodul: "The Hostages" |
| Doc | Jeff / George | Episodul: "A Little Bit of Soap" |
| Rhoda | Jerry Blocker | Episodul: "Attack on Mr. Right" |
| Phyllis | Paul Jameson | Episodul: "The New Job" |
| 1977–1984 | Three's Company | Jack Tripper | rol principal (174 episoade) |
| 1977 | The Love Boat | Dale Riley / Dale Reinhardt | Episodul: "Oh, Dale" |
| 1978 | Ringo | Marty Flesh | film de televiziune |
| Leave Yesterday Behind | Paul Stallings |
| 1979 | The Ropers | Jack Tripper | Episodul: "The Party" |
| 1980 | The Associates | Chick | Episodul: "The Censors" |
| The Comeback Kid | Bubba Newman | film de televiziune |
| John Ritter: Being of Sound Mind and Body | El însuși/ Personaje diverse | special TV |
| 1981 | Insight | Frankie | Episodul: "Little Miseries" |
| 1982 | Pray TV | Tom McPherson | film de televiziune |
| In Love with an Older Woman | Robert Christenberry |
| The Fantastic Miss Piggy Show | El însuși (invitat - apariție specială) | special TV |
| 1983 | Sunset Limousine | Alan O'Black | film de televiziune |
| The Love Boat | Ben Cummins | Episodul: "The Emperor's Fortune" |
| 1984 | Love Thy Neighbor | Danny Loeb | film de televiziune |
| Pryor's Place | El însuși (invitat - apariție specială) | Episodul: "The Showoff" |
| 1984–1985 | Three's a Crowd | Jack Tripper | rol principal (22 episoade) |
| 1985 | Letting Go | Alex Schuster | film de televiziune |
| 1986 | Unnatural Causes | Frank Coleman |
| A Smoky Mountain Christmas | Judge Harold Benton |
| Life with Lucy | El însuși (invitat - apariție specială) | Episodul: "Lucy Makes a Hit with John Ritter" |
| 1987 | The Last Fling | Phillip Reed | film de televiziune |
| Prison for Children | David Royce |
| 1987–1989 | Hooperman | Det. Harry Hooperman | rol principal (42 episoade) |
| 1988 | Mickey's 60th Birthday | Dudley Goode | special TV |
| Tricks of the Trade | Donald Todsen | film de televiziune |
| 1989 | Have Faith | Rick Shepherd | Episodul: "The Window" |
| My Brother's Wife | Barney Rusher | film de televiziune |
| 1990 | Stephen King's It | Ben Hanscom | miniserial TV |
| The Dreamer of Oz: The L. Frank Baum Story | L. Frank Baum | film de televiziune |
| 1991 | The Cosby Show | Ray Evans | Episodul: "Total Control" |
| The Summer My Father Grew Up | Dr. Paul Saunders | film de televiziune |
| Anything but Love | Patrick Serreau | rol secundar(5 episoade) |
| 1992 | Fish Police | Inspector Gill (voce) | rol principal (6 episoade) |
| 1992–1995 | Hearts Afire | John Hartman | rol principal (54 episoade) |
| 1993 | Heartbeat | Bill Grant | film de televiziune |
| The Only Way Out | Jeremy Carlisle |
| The Larry Sanders Show | El însuși (invitat - apariție specială) | Episodul: "Off Camera" |
| 1994 | Dave's World | John Hartman | Episodul: "Please Won't You Be My Neighbor" |
| 1995 | Gramps | Clarke MacGruder | film de televiziune |
| The Colony | Rick Knowlton |
| NewsRadio | Dr. Frank Westford | Episodul: "The Shrink" |
| The Larry Sanders Show | El însuși (invitat - apariție specială) | Episodul: "The Fourteenth Floor" |
| 1996 | Unforgivable | Paul Hegstrom | film de televiziune |
| Wings | Stuart Davenport | Episodul: "Love Overboard" |
| For Hope | Date #5 | film de televiziune (nemenționat)[necesită citare] |
| Touched by an Angel | Mike O'Connor / Tom McKinsley | 2 episoade |
| 1997 | Loss of Faith | Bruce Simon Barker | film de televiziune |
| A Child's Wish | Ed Chandler |
| Dead Man's Gun | Harry McDonacle | Segment: "The Great McDonacle" |
| Over the Top | Justin Talbot | Episodul: "The Nemesis" |
| Buffy the Vampire Slayer | Ted Buchanan | Episodul: "Ted" |
| 1997–2004 | King of the Hill | Eugene Grandy (voce) | 4 episoade |
| 1998 | Chance of a Lifetime | Tom Maguire | film de televiziune |
| Ally McBeal | George Madison | 2 episoade |
| Dead Husbands | Dr. Carter Elston | film de televiziune |
| 1999 | Veronica's Closet | Tim | Episodul: "Veronica's Favorite Year" |
| Holy Joe | Rev. Joe Cass | film de televiziune |
| It Came from the Sky | Donald Bridges |
| Lethal Vows | Dr. David Farris |
| 2000–2003 | Clifford the Big Red Dog | Clifford (voce) | rol principal (64 episoade) |
| 2000-2003 | Seven Little Monsters | Three (voce normală) | în câteva epsioade (nemenționat) |
| 2000 | Chicago Hope | Joe Dysmerski | Episodul: "Simon Sez" |
| Batman Beyond | Dr. David Wheeler (voce) | Episodul: "The Last Resort" |
| Family Law | Father Andrews | Episodul: "Possession is Nine Tenths of the Law" |
| 2000–2002 | Felicity | Mr. Andrew Covington | rol secundar (7 episoade) |
| 2001 | Tucker | Marty | Episodul: "Homewrecker for the Holidays" |
| 2002 | The Ellen Show | Percy Moss | Episodul: "Gathering Moss" |
| Law & Order: Special Victims Unit | Dr. Richard Manning | Episodul: "Monogamy" |
| Breaking News | Lloyd Fuchs | Episodul: "Pilot" |
| Scrubs | Sam Dorian | 2 episoade |
| 2002–2003 | 8 Simple Rules for Dating My Teenage Daughter | Paul Hennessy | rol principal (31 episoade) |
