| Year | Title | Role | Notes |
| 1953 | Juke Box Jury | Himself | Unknown episodes |
| 1957 | The Dinah Shore Chevy Show | Himself | One episode |
| 1963 | The Eleventh Hour | Kenny Walsh | Episode: "And God Created Vanity" |
| 1966 | Bob Hope Presents the Chrysler Theatre | Lt. Commander Nick Raino / Harry Brophy | Episodes: "The Enemy on the Beach" and "Runaway Bay" |
| 1967 | How I Spent My Summer Vacation | Jack Washington | Television movie |
| 1968–1970 | It Takes a Thief | Alexander Mundy | 66 episodesNominated – Primetime Emmy Award for Outstanding Lead Actor in a Drama Series (1970)Nominated – Golden Globe Award for Best Actor – Television Series Drama (1970) |
| 1970 | The Name of the Game | Nick Freitas | Episode: "The War Merchants" |
| The Red Skelton Hour | Colossal Boy | Episode: "The Family Business" |
| 1971 | The Name of the Game | Dave Corey | Episode: "The Man Who Killed a Ghost" |
| City Beneath the Sea | Brett Matthews | Television movie |
| Crosscurrent / The Cable-Car Murder | Howard McBride | Television movie |
| Perlico - Perlaco | Robert Wagner | Television movie |
| 1972 | Killer by Night | Dr. Larry Ross | Television movie |
| The Streets of San Francisco | David J. Farr | Episode: "Pilot" |
| 1972–1974 | Colditz | Flight Lieutenant Phil Carrington | 14 episodes |
| 1973 | The Affair | Marcus Simon | Television movie |
| 1975 | The Abduction of Saint Anne | Dave Hatcher | Television movie |
| 1975–1978 | Switch | Pete T. Ryan | 71 episodes |
| 1976 | Death at Love House | Joel Gregory (Jr. & Sr.) | Television movie |
| Laurence Olivier Presents | Brick | Episode: "Cat on a Hot Tin Roof" |
| 1977 | The Hardy Boys/Nancy Drew Mysteries | Himself | Episode: "The Mystery of the Hollywood Phantom: Part II" |
| 1978 | The Critical List | Dr. Nick Sloan | Television movie |
| Pearl | Capt. Cal Lankford | Television miniseries |
| 1979–1984 | Hart to Hart | Jonathan Hart | 111 episodesNominated – Golden Globe Award for Best Actor – Television Series Drama (1980)Nominated – Golden Globe Award for Best Actor – Television Series Drama (1981)Nominated – Golden Globe Award for Best Actor – Television Series Drama (1983)Nominated – Golden Globe Award for Best Actor – Television Series Drama (1984) |
| 1980 | The Jacques Cousteau Odyssey | Narrator | 2 episodes |
| 1981 | The Fall Guy | Himself | Episode: "The Meek Shall Inherit Rhonda" |
| 1984 | To Catch a King | Joe Jackson | Television movie |
| 1985–1986 | Lime Street | James Greyson Culver | 8 episodes |
| 1986 | There Must Be a Pony | Ben Nichols | Television movie |
| 1987 | Love Among Thieves | Mike Chambers | Television movie |
| 1988 | Windmills of the Gods | Mike Slade | Television miniseries |
| Indiscreet | Philip Adams | Television movie |
| 1989 | Around the World in 80 Days | Alfred Bennett | Television miniseries |
| 1991 | This Gun for Hire | "Raven" | Television movie |
| False Arrest | Ron Lukezic | Television movie |
| 1992 | Jewels | Charles Davenport | Television miniseries |
| 1993 | Les audacieux | Charles Madigan | Television movie |
| 1993-1996 | Hart To Hart | Jonathan Hart | Eight television movies |
| 1994 | Parallel Lives | Sheriff | Television movie |
| The Arsenio Hall Show | Himself | One episode |
| North & South: Book 3, Heaven & Hell | Cooper Main | Television miniseries |
| 1995 | Cybill | Jonathan Hart | UncreditedEpisode: "Virgin, Mother, Crone" |
| 1997 | Seinfeld | Dr. Abbot | Episode: "The Yada Yada" |
| 1999 | Fatal Error | Albert Teal | Television movie |
| Camino de Santiago | William Derek | Television miniseries |
| 2000 | Rocket's Red Glare | Gus Baker | Television movie |
| Becoming Dick | Edward | Television movie |
| 2001 | The Retrievers | Durham Haysworth | Television movie |
| 2003 | A Screwball Homicide | Sheldon Bennett | Television movie |
