After studying law, he turned to acting in the mid-1990s with small roles in productions such as Mrs Brown (1997), the James Bond film Tomorrow Never Dies (1997), and Tale of the Mummy (1998).

Butler gained wider recognition for his portrayal of King Leonidas in Zack Snyder's fantasy war film 300 (2007).

[9] A year later, when his parents' marriage broke down, his mother left Montreal and returned to Scotland with Gerard, aged 18 months.

"[10] Initially unable to win any acting roles, he worked in a variety of jobs including as a waiter, a telemarketer and a toy demonstrator at fairs.

At age 30, he decided to move to Los Angeles, where he won parts in Dracula 2000, Tomb Raider 2, Dear Frankie and Phantom of the Opera.

[14] In London, Butler had various odd jobs until being cast by actor and director Steven Berkoff (who later appeared alongside him in Attila (2001)) in a stage production of Coriolanus.

He was cast as Ewan McGregor's character Renton in the stage adaptation of Trainspotting, the same play that had inspired him to become an actor.

[19] He then appeared in Reign of Fire (2002)[20] as Creedy and Lara Croft: Tomb Raider – The Cradle of Life (2003) as Terry Sheridan, alongside Angelina Jolie.

In the role of Andre Marek in the big-screen adaptation of Michael Crichton's novel Timeline (2003),[21] Butler played an archaeologist who was sent back in time with a team of students to rescue a colleague.

[26] In 2007, he appeared in Butterfly on a Wheel co-starring Pierce Brosnan and Maria Bello, which aired on network TV under the title Shattered,[27] and in the romantic comedy P.S.

[30] In 2010 he starred in the action/comedy The Bounty Hunter with Jennifer Aniston,[31] and did voice acting for the 2010 animated film How to Train Your Dragon as Stoick the Vast.

[32] On 15 and 16 October 2010, thanks to the popularity of his role as Spartan King Leonidas and the use of his lines during athletic events at Michigan State University, he was a guest at their Midnight Madness and homecoming American football game.

[33] As of August 2011[update], Butler, while filming Playing for Keeps, was writing songs and in the process of recording an album.

[35] On 18 December that year, while filming Chasing Mavericks, Butler was hospitalized after he was pulled under big waves.

[36] Butler starred as Secret Service agent Mike Banning in the action thriller Olympus Has Fallen (2013), opposite co-stars Aaron Eckhart and Morgan Freeman.

He starred as Mike Banning again in the 2019 film Angel Has Fallen and returned as the voice of Stoick in How to Train Your Dragon: The Hidden World, which was released the same year.

In January 2024, Butler was announced to reprise his role as Stoick in the live-action remake of How to Train Your Dragon, which is set for a 2025 release.

[47] In August 2013, he bought an equity stake in the Jamaica Tallawahs cricket team, part of the Limacol Caribbean Premier League (CPL).