While attending College in Luton, Arnold became friends with director Danny Cannon. The two made their respective major film debuts with The Young Americans. Play Dead, a song from the film with singer Björk, charted #12 in the UK. The following year he scored Stargate and Last of the Dogmen.

Arnold would then go on to compose music for Stargate-director Roland Emmerich’s next two movies, Independence Day and Godzilla, as well as four movies for director John Singleton. In addition, he has also scored various comedies, dramas, and nineteenth-century period pieces, as well as providing music for several British television shows including the 2000 remake of Randall and Hopkirk and Little Britain. During film production, his compositions are conducted by Nicholas Dodd. In 2010, he composed the music for Come Fly With Me, a British television series from the producers of Little Britain.

Arnold was a Bond fan from an early age and also a fan of Bond composer John Barry. In 1997, Arnold produced »Shaken and Stirred: The David Arnold James Bond Project«, an album featuring new versions of the themes from various James Bond films. John Barry, the composer of many of the themes on the album was complimentary about Arnold’s interpretation of his work and thus contacted Barbara Broccoli, producer of the then-upcoming Tomorrow Never Dies, to recommend Arnold as the film’s composer.
Arnold was hired to score the installment, and he has since scored the four subsequent films: The World Is Not Enough, Die Another Day, Casino Royale and Quantum of Solace.
Arnold also co-wrote the main theme songs for The World Is Not Enough (The World Is Not Enough by Garbage) and Casino Royale (You Know My Name by Chris Cornell).

Arnold is the second cousin of Irish singer-songwriter Damien Rice and is an ambassador for the aid agency CARE International in the UK. In February 2011 he was appointed Musical Director for the 2012 Olympic Games and the 2012 Paralympic Games in London.