He was born Lamine Secka in Dakar, Senegal to a Wolof family, the youngest of five siblings; his Gambian father died shortly after his birth.

He also appeared on television, in programmes such as The Human Jungle, Z-Cars, Dixon of Dock Green, Gideon's Way, Danger Man, and a 1968 episode of The Avengers.

He was seen as a British equivalent to Sidney Poitier, and was frustrated that actors who started out at around the same time as him – such as Sean Connery, Terence Stamp, Michael Caine, Tom Courtenay and John Hurt – had become stars, and he had not.

Sekka is widely known among science fiction fans for his role as Dr. Benjamin Kyle in the television series Babylon 5's pilot movie, The Gathering (1993).

Recurring health problems forced him to decline a future role in the series, and ultimately were the reason he retired from acting altogether.

On 14 September 2006, Sekka died of lung cancer at his ranch in Agua Dulce, California, aged 72, survived by his wife Cecilia and son Lamine.