Vosloo was born in Pretoria, South Africa into an acting family, his parents being stage-actors, thus the family moved around quite a lot. They lived in Port Elizabeth, where his father ran a drive-in theatre, and Alberton.

Vosloo began his acting career in the South African theatre where he won several Dalro Awards for his performances in such plays as Don Juan, Hamlet, and Môre is 'n Lang Dag (Tomorrow is a Long Day) and he quickly became a regular at Pretoria's State Theatre. He also starred in Torch Song Trilogy and won another award for the TV show Meisie van Suid-Wes (Girl from South-West-Africa).

In 1984, he moved on to film, where he continued Dalro Award-winning performances in films such as Boetie gaan Border toe (Little brother goes to the border, a comedy about the Border War), and Circles in a Forest (based on the book Kringe in 'n Bos by author Dalene Matthee) in 1990. Vosloo also starred in the "Boetie" sequel, Boetie op maneuvers (Boetie on maneuvers) in 1986, in Morenga (1985), Saturday Night at the Palace (based on the play by Paul Slabolepszy about racism in South Africa), Skeleton Coast (1987) and The Rutanga Tapes (1990).

Upon arriving in the U.S., Vosloo returned to the theatre where he appeared in Born In The R.S.A. at Chicago's Northlight Theatre and in the NY's Circle In The Square Uptown's short-lived production of Salomé (1992) together with Al Pacino

His American movie debut was in 1492: Conquest of Paradise (1992). He later appeared in the two less successful sequels to the 1990 film Darkman — Darkman II: The Return of Durant (1994) and Darkman III: Die Darkman Die (1996), filling the shoes of Liam Neesonas the titular character Darkman. He also starred in the John Woo film Hard Target, starring Jean-Claude Van Damme. Vosloo appeared in the title role of the 1999 movie The Mummy (starring Brendan Fraser, as well as its 2001 sequel, The Mummy Returns. In both films he played Imhotep, an ancient Egyptian high priest.

Alongside his film career, he guest-starred in several TV shows including The Red Shoe Diaries, American Gothic (1995), Nash Bridges (1995), Charmed (2000), and Alias (2004). He was one of the main characters in Veritas: The Quest (2003). He also had a major role in the fourth season of 24 (2005), as terrorist leader Habib Marwan.

In 2004, Vosloo returned to South Africa to make Forgiveness, about an ex-policeman who seeks out the family of the anti-Apartheid activist that he killed. His most recent film role was his role as the mercenary, Colonel Coetzee, in the 2006 film Blood Diamond which was partially filmed in South Africa.