Baptiste was born in British Guiana (now Guyana) as the son of a wealthy landowner. He moved to Britain in the late 1940s. His one contact was the Labour MP Tom Driberg, who helped him gain factory employment, and Baptiste enrolled at Morley College in Lambeth to study music followed by scholarships to the National School of Opera and Royal Academy of Music. Baptiste joined Joan Littlewood's Theatre Workshop early in its existence.
Baptiste appeared in a production of Noël Coward's Nude with Violin for two years from 1956 with John Gielgud, Patience Collier and Kathleen Harrison, first in Dublin and then the West End. In 1960 he played Riley in the first professional production of Harold Pinter's The Room and in a production directed by Pinter himself who had wanted to cast Baptiste in the role. It became an episode of ITV's Television Playhouse broadcast in October 1961. In 1963 Baptiste played the first Black character to appear in Coronation Street, a bus conductor who was falsely sacked as a result of a racist altercation with Len Fairclough. Fable (1965) was an edition of The Wednesday Play series by John Hopkins which imagined Britain as a mirror apartheid society. The Alun Owen drama Pal (Play for Today, 1971), of which no recording survives, was the first British television play to feature a black gay character. Meanwhile on stage during the 1960s, he played Doolittle in Pygmalion and George in Who's Afraid of Virginia Woolf?. Later, he played Paul Robeson, who he admired greatly, in Are You Now or Have You Ever Been? at the Birmingham Rep in 1978, a production which transferred to Mayfair.
In the 1960s, he co-founded an advisory committee of the British Actors' Equity Association, to represent black actors in Britain. In an interview which appeared in 1992, Baptiste said that he thought black actors were having even more difficulty beginning their careers than he had done forty years earlier.
- Nude with Violin (as Obadiah Lewellyn)
- Who's Afraid of Virginia Woolf? (as George)
- Pygmalion (as Alfred Doolittle)
- Are You Now or Have You Ever Been? 1978 Birmingham Rep (as Paul Robeson)
- Sapphire (1959) - Man on the Street (uncredited)
- Beyond This Place (1959) - Haydock
- Flame in the Streets (1961) - (uncredited)
- In the Cool of the Day (1963) - Murray Logan's chauffeur (uncredited)
- Guns at Batasi (1964) - Minor Role (uncredited)
- Dr. Terror's House of Horrors (1965) - Dambala (segment "Voodoo") (uncredited)
- The Ipcress File (1965) - Barney - American Agent
- Help! (1965) - Bandsman (uncredited)
- Jemima & Johnny (1966, Short) - Jemima's Father
- The Comedians (1967) - Haitian Soldier (uncredited)
- The Seven Red Berets (1969) - Africian soldier (uncredited)
- Two Gentlemen Sharing (1969) - Mutt, Moving Man
- Sunday Bloody Sunday (1971) - Prof. Johns
- Divorce His, Divorce Hers (1973, TV Movie) - Minister
- Black Snake (1973) - Isiah
- Shaft in Africa (1973) - Kopo
- Ghost in the Noonday Sun (1973) - Andullah
- Honeybaby, Honeybaby (1974) - Gen. Christian Awani
- The Wild Geese (1978) - Col. Mboya
- The Class of Miss MacMichael (1978) - Visitor
- The Music Machine (1979) - Claire's Father
- The Dogs of War (1980) - Dexter
- Rise and Fall of Idi Amin (1981) - Dr. Michael Oloya
- Ama (1991) - Babs
- The Secret Laughter of Women (1999) - Papa Fola
- Nightfall at Kriekville (1961) - Bantu Parson
- Coronation Street (1963) - Johnny Alexander
- Fable (The Wednesday Play, 1965) - Mark
- Till Death Us Do Part (intolerance) 1966
- Pal (1971)
- Empire Road (1978-1979) - Herbie
- Yes Minister (1980) - President Selim Mohammed
- Minder (high drains pilferer) (1984) - Mr. Mikabwe
- King (1984) - Mr. King
- Drums Along Balmoral Drive (1986) - Badinga
- EastEnders (1990)
- Love Hurts (1992) - Lord Godfrey
- Whyte, Seb. "Baptiste, Thomas (1936-)". Screenonline. BFI. Retrieved 30 May 2014.
- Coveney, Michael (12 December 2018). "Thomas Baptiste obituary". The Guardian. Retrieved 12 December 2018.
- "Thomas Baptiste obituary". The Times. 10 January 2019. Retrieved 10 January 2019. (subscription required)
- Taylor-Batty, Mark (2014). The Theatre of Harold Pinter. London: Bloomsbury Methuen Drama. p. 274, n.1:5.
- Iqbal, Nosheen (8 January 2009). "Old times: actors remember Harold Pinter". The Guardian.
- Malik, Sarita (2002). Representing Black Britain: Black and Asian Images on Television. London: Sage. p. 141.
- Cochrane, Claire (2011). Twentieth-Century British Theatre: Industry, Art and Empire. Cambridge: Cambridge University Press. p. 225.