McCormack was born in Freetown to Sierra Leone Creole parents.

[1] He lived in Nigeria and Kenya before attending SUNY Purchase in New York.

[1] He has appeared in numerous TV-series, and he portrayed a recurring character on Lost as Mr. Eko's deceased brother, Yemi.

He played Zeze Eto'o in 24 during season 7, episodes 4 and 5, and the recurring antagonist Isaac on Castlevania.

His first feature film was the Academy award-nominated Blood Diamond (2006).