His first film role was in Dr. Strangelove in 1964. He has appeared in many roles since, but is probably best known as the sonorous voice of Darth Vader in the Star Wars films, Mufasa in The Lion King, a Disney animated feature, and CNN tagline, "This is CNN". He has performed considerable amounts of other voice-over work. He has also periodically performed guest voices on television's The Simpsons. He also starred in the television program Under One Roof as Neb Langston, a widowed police officer. He is a sponsor of Verizon Wireless.
He won Tony awards in 1959 in The Great White Hope and in 1987 in Fences. He received Kennedy Center Honors in 2002.