Born in Scotland but raised in France, Macfadyen began his performing career as a child clown in a circus. He returned to Scotland to attend college and moved to London to attend drama school. He began making appearances with the Edinburgh Fringe Theatre, featured in such productions as "The Tempest" and "The Immortals". In 1991, his play "1905", which he has described as a sequel of sorts to Chekhov's "Uncle Vanya" won the Questor Award.

Macfadyen found frequent employment in British TV productions ranging from the Scottish series "Soldier, Soldier" to "The Lost Language of Cranes" (1992). In the latter, based on David Leavitt's novel, he was cast as Philip Benjamin, the gay son whose disclosure of his homosexuality leads to revelations about his father (Albert Finney). When the telefilm aired on PBS in the USA, it caused some controversy for brief nudity; a slightly edited version aired in some markets. The actor subsequently portrayed actor Richard Burton--to whom he bears a striking resemblance--in the unauthorized biopic "Liz: The Elizabeth Taylor Story" (NBC, 1995).

With his "Braveheart" performance as a direct ancestor of the current British royal family who eventually leads the Scottish commoners and nobles to independence, Macfadyen displayed both a magnetic screen presence and dramatic versatility. He next portrayed a German prisoner-of-war held in an Irish internment camp in "The Brylcreem Boys" (1996). Subsequently, he was cast as an art gallery owner conned by Joanna Going in "Still Breathing", played Amy Brenneman's estranged husband in the low-key thriller "Nevada" and was suitable villainous (although slightly over the top) as a warlord in the kidflick "Warriors of Virtue" (all 1997). Macfadyen next appeared as Orson Welles in Tim Robbins' ambitious period drama "Cradle Will Rock" and as Anthony Hopkins' son Lucius in "Titus" (both 1999).