| Year | Title | Role | Other Notes |
|---|
| 1958–1961 | Alfred Hitchcock Presents | Lloyd Ashley & DA Rudolph Cox | Two episodes |
| 1959 | The Swamp Fox | Colonel Francis Marion | |
| 1960 | Thriller | Alan Patterson (lead role) | Episode "The Twisted Image" |
| 1961 | The New Breed | Lt. Price Adams | Regular |
| 1963 | Channing | Professor Paul Stafford | Single episode |
| 1964 | Your First Impression | As himself | Single episode |
| 1964 | The Alfred Hitchcock Hour | Steven Grainger | Single episode |
| 1964–1969 | The Virginian | Ben Stratton | Five episodes |
| 1967 | Bonanza | Sheriff Paul Rowan | One episode |
| 1969 | The Bold Ones: The Protectors | Deputy Police Chief Sam Danforth | Seven episodes |
| 1969–1974 | Hawaii Five-O | Brent & Colonel Faraday | Two episodes |
| 1971–1975 | Columbo | Peter Hamilton & Geronimo | Two episodes |
| 1971 | Bearcats! | Col. Ted Donovan | Single episode |
| 1971 | Night Gallery | Col. Dennis Malloy | Single episode "A Question of Fear" |
| 1973 | M*A*S*H | Col. Buzz Brighton | Episode "The Ringbanger" |
| 1973–1974 | The Streets of San Francisco | Ofc. Joe Landers, Insp. John T. Connor, & Big Jake Wilson | Three episodes |
| 1974 | Cannon | Eric Strauss | Single episode |
| 1975 | Kung Fu | Vincent Corbino | Four episodes |
| 1979 | Backstairs at the White House | Ike Hoover | Three episodes |
| 1982 | Police Squad! | Det. Frank Drebin | |
| 1984 | Shaping Up | Buddy Fox | |
| 1985–1986 | Murder, She Wrote | Captain Daniels & David Everett | Two episodes |
| 1988 | Who's The Boss | Max | |
| 1988 | Day By Day | Jack Harper | One episode, nominated for an Emmy Award |
| 1989 | Saturday Night Live | Himself | Single episode |
| 1992 | The Golden Girls | Lucas Hollingsworth | Series finale |
| 1994–1999 | Due South | Sgt. Buck Frobisher | Four episodes |
| 1994–1996, 2001–2002 | Katie and Orbie | Narrator | |
| 1995 | Mr. Willowby's Christmas Tree | Mr. Willowby's Butler, Baxter | Television Christmas special |
| 2000 | Santa Who? | Santa Claus | Television film |
| 2001 | Scrubs | cross-dresser | Uncredited |
| 2002 | Liocracy | Terrence Brynne McKennie | |
| 2004 | Zeroman | Les Mutton/Zeroman | |
| 2007 | Doctorology | Himself, Host | |
| Lipshitz Saves the World | Lipshitz's mentor | Pilot |
| Robson Arms | Cado Vasco | |