| Year | Title | Role | Notes | Ref. |
| 1963 | The Avengers | Young Man | Episode: "Don't Look Behind You" | |
| Thorndyke | Ellis | 1 episode | |
| 1964 | The Other Man | Colin | Part of the Play of the Week series | |
| 1970 | Dance of the Seven Veils | Hitler | TV film | |
| 1970–1972 | A Family at War | Sergeant Jago | | |
| 1971 | The Rivals of Sherlock Holmes | Farrish | 2 episodes | |
| 1974 | The Nine Tailors | "Potty" Peake | TV mini-series (part of Lord Peter Wimsey), Series 1 Episode 3 | |
| Special Branch | Oliver | TV series, Series 4 Episode 9, "Date of Birth" | |
| Fall of Eagles | Father Gapon | Episode: "Dearest Nicky" | |
| 1975 | The Sweeney | Noah Riley | TV series, Series 2 Episode 6, "Trap" | |
| 1977 | Ripping Yarns | Arthur, The Robber | Episode: "The Testing of Eric Outhwaite" | |
| 1978 | Les Misérables | Police Prefect | TV film | |
| Pennies from Heaven | The Accordion Man | 6 episodes, TV mini-series | |
| 1979 | Measure for Measure | Duke | TV film, part of the BBC Television Shakespeare series | |
| The Danedyke Mystery | Major | 6 episodes, TV series | |
| 1982 | I Remember Nelson | Admiral Lord Nelson | TV mini-series | |
| 1985 | Wallenberg: A Hero's Story | Adolf Eichmann | TV film | |
| Mussolini: The Untold Story | King Victor Emmanuel III of Italy | TV mini-series | |
| 1986 | Return to Treasure Island | Ben Gunn | 10 episodes, credited as Ken Colley | |
| 1987 | Casanova | Le Duc | TV film | |
| 1988 | War and Remembrance | SS Standartenführer Paul Blobel | 2 episodes, TV mini-series | |
| 1990 | Agatha Christie's Poirot | Mathew Davenheim | Episode: "The Disappearance of Mr. Davenheim" | |
| 1991 | Minder | Ron the Burglar | Episode: "Him Indoors" | |
| Inspector Morse | DCI Patrick Dawson | Episode: "Second Time Around" | |
| Prisoner of Honor | Captain Alfred Dreyfus | TV film | |
| 1992 | The Secret Life of Arnold Bax | John Ireland | TV film | |
| 1993 | Unnatural Causes | Inspector Gerry Reckless | TV film | |
| Between the Lines | Chief Supt. Tattersall | Episode: "Manoeuvre 11" | |
| 1994–1995 | Moving Story | Ken Uttley | 13 episodes | |
| 1995 | Solomon & Sheba | Nathan | TV film | |
| 1996 | Wycliffe | Sam Peploe | Episode: "Number of the Beast" | |
| 1995–1999 | The Bill | Various characters | 3 episodes, credited as Ken Colley in 1999 | |
| 1999 | The Last Train | Mark | Episode Five, credited as Ken Colley | |
| 2000 | Casualty | Clifford Watkins | Episode: "The Turning of the Scrooge" | |
| 2001 | Midsomer Murders | Lloyd Kirby | Episode: "The Electric Vendetta" | |
| 2002 | Relic Hunter | Professor Lamenza | Episode: "Faux Fox" | |
| 2003 | EastEnders | Brian | 3 episodes | |
| 2005 | Like Father Like Son | Rawsthorne | 2 episodes | |
| 2006 | Foyle's War | Brian Jones | Episode: "Bad Blood" | |
| New Tricks | Frank Benson | Episode: "Dockers" | |
| 2009 | Casualty 1909 | Dr. Frederick Smith | 3 episodes | |
| 2012 | Lego Star Wars: The Empire Strikes Out | Admiral Piett (voice) | TV film, credited as Kenneth Cooley | |
| 2013 | Vera | Ronald Devreux | Series 3, Episode 3 Young Gods | |
| Misfits | Old Rudy | Series 5, Episode 4 | |
| 2016 | Peaky Blinders | Vicente Changretta | Series 3, Episodes 2 & 3 | |