One of his earliest big screen roles was in Jude (1996), in which he shared a scene with his Doctor Who predecessor Christopher Eccleston, playing a drunken undergraduate who challenges Eccleston's Jude to prove his intellect.He has lent his voice to several supporting characters in Big Finish audio plays based on the 1963 version of Doctor Who.
He made his first, brief appearance in the episode The Parting of the Ways (2005) after the regeneration scene, and also appeared in a special 7-minute mini-episode shown as part of the 2005 Children in Need appeal, broadcast on 18 November 2005 (coincidentally the same day Harry Potter and the Goblet of Fire, in which he played Barty Crouch Jr., was released to theatres).
While Eccleston holds the distinction of being the first man to play the Doctor not even born when the series premiered, Tennant is the first Doctor who was not even conceived, as Eccleston was born during the first season.
He got a chance to have a peripheral connection to the series when he narrated a prelude episode of Doctor Who Confidential that aired prior to the broadcast of Rose.
With Eccleston's announcement on 30 March that he would not be returning for a second series, the BBC confirmed Tennant as his replacement in a press release on 16 April.
He has appeared in several high-profile dramas for the BBC, including Takin' Over the Asylum, (1994) a six part BBC Scotland serial in which he played a manic depressive named Campbell, He Knew He Was Right (2004), Blackpool (2004), Casanova (2005) and The Quatermass Experiment (2005).
In film, he has appeared in Stephen Fry's Bright Young Things, and as Barty Crouch Jr in Harry Potter and the Goblet of Fire, alongside Roger Lloyd Pack who played John Lumic in Rise of the Cybermen and The Age of Steel, and Michael Gambon.
He has often expressed enthusiasm about fulfilling his childhood dream.
He remarked to an interviewer for GWR FM, "Who wouldn't want to be the Doctor? " Like Peter Davison before him, Tennant was knowledgeable enough about the program to ask for his character to be credited as "The Doctor" instead of "Doctor Who", as had been done during Eccleston's tenure.
His first story was Colditz (also guest starring Tracey Childs, who later appeared in The Fires of Pompeii), where he played the German officer Kurtz.
He later played two versions of Ross Brimmicombe-Wood in Sympathy for the Devil and the UNIT story The Wasting, Daft Jamie in Medicinal Purposes, a Time Lord in Exile and Galanar in the third series of Dalek Empire.
Tennant began filming the new series of Doctor Who in late July 2005.