Making his American television debut in 1992 on the daytime soap Another World, Australian-born McMahon continued his TV run as a series regular on the WB favorite Charmed.
However, his fan favorite character was killed off on the show's 100th episode.
In 2005, McMahon was featured in the first installment of the film adaptation of the Fantastic Four comic book as Victor Von Doom. He reprised his role for the film's sequel, Fantastic Four and the Silver Surfer and can also be seen in the film Premonition opposite Sandra Bullock.
The actor was recently lauded for his small screen accomplishments when he was nominated for a Golden Globe Award for Best Actor in a Drama Series in 2005.
McMahon was married to Australian singer/actress Danii Minogue, with whom he costarred in the Australian drama Home and Away, from 1994-1995.
A marriage to actress Brooke Burns followed, lasting from 1999-2001. McMahon and Burns have one daughter together.