I n 1972, Paul Winfield, who has died aged 62 from a heart attack, became the third African-American actor to be nominated for an Oscar. It was for his role as Nathan Morgan in Martin Ritt's critically acclaimed Sounder, one of those rare films about the black experience which achieved a substantial crossover into the mainstream market .

Winfield played Nathan Morgan opposite Cicely Tyson (who was also nominated for an Oscar) as his wife in a work which stood out against the tide of blaxploitation movies released at the time. It was a thoughtful, positive take on a loving African-American sharecropping family in 1930s Louisiana.

For much of his career Winfield was a character actor. Since, as he observed, he was not "particularly pretty" and he could not sing or dance, he started off in television with minor roles as black activists or psychopathic heavies. But from 1968 to 1970 Winfield played Diahann Carroll's boyfriend in the television comedy series Julia - the first network show to star a black woman.

It was Sidney Poitier who got Winfield his first credited movie role in The Lost Man (1969), in which Poitier starred. Winfield was to go on to appear in scores of films, television productions and on stage, taking in films such as Star Trek: The Wrath Of Khan (1982), The Terminator (1984), Cliffhanger (1993), and Mars Attacks! (1996), and shows ranging from The High Chapparal (1969) and LA Law (1990) to Teen Angel (1997).

In 1978 and 1979, he was nominated for an Emmy for his performance as Martin Luther King Jr in the television series King, and as a college administrator in Roots: The Next Generation. He finally won an Emmy in 1995 for his guest appearance as a judge in Picket Fences.

Four years later, in Strange Justice, he portrayed the first African-American Supreme Court justice, Thurgood Marshall. His last TV appearance was as the teacher in a 2003 remake of Sounder.

Born in Los Angeles, California, he was bought up by a union leader mother and construction worker stepfather. He was, he later recalled, taken to see a psychiatrist when he was three. He was not a particularly disturbed child, he added, but he was not a normal one either.

In 1949, the eight-year-old Winfield saw Mark Robson's groundbreaking Home Of The Brave, a drama about racism in the US army. It broke a Hollywood taboo by prominently featuring black actor James Edwards, and Winfield said the film inspired him to become a performer.

His parents' response to Edwards' performance had a galvanising effect on Winfield. "He wasn't the porter, the servant. It was a soldier, somebody they could look up to. It was a real revelation."

Winfield spent part of his formative years in Portland, Oregon, where segregation was rife. He also suffered racism on his return to Los Angeles. He was bussed to Manual Arts High School, a majority-white school, whose liberal drama teacher, Reuben Plaskoff, encouraged the young Winfield to take up acting.

Turning down a Yale scholarship, he accepted a scholarship to study theatre arts at the University of Portland, Oregon, and later at the University of California. In 1966, he got his first break while a contract actor with Columbia Pictures, when Burgess Meredith cast him in two plays by the controversial playwright and poet Amiri Baraka (then LeRoi Jones), Dutchman and The Toilet.

A civil rights campaigner, he has been inducted into the Black Filmmakers Hall of Fame and won an Image Award by the National Association for the Advancement of Colored People.

At the time of his death he was the narrator for the cable TV series City Confidential. His partner of many years, Charles Gillian Jr, predeceased him. He is survived by a sister, Patricia Wilson.

· Paul Winfield, actor, born May 22 1941; died March 7 2004

Paul E Winfield