Gruffudd began his acting career at a age of Xiv in the Welsh soap opera Pobol y Cwm (People of the Vale). Aged 18 he attended a Royal Academy of Dramatic Art (RADA). He won his number 1 major English language role a few years late in the 1996 TV remaking of Poldark.

When swimming Oscar Wilde's gay lover in Wilde within 1997, he got his 1st international role when Fifth Officer Harold Godfrey Lowe in the blockbuster film Titanic. He late had his right-known role when Horatio Hornblower in the ITV production of the C.S. Forester novels. Next, he played Pip in the BBC production of Charles Dickens' Great Expectations. He has besides starred within 102 Dalmatians, ITV's adaptation of The Forsyte Saga, Black Hawk Down, King Arthur and most recently Fantastic Four.

Selected Filmography
|- bgcolor="#CCCCCC" ! Season !! Film !! Role |- | 2006 || Amazing Grace || William Wilberforce |- | 2006 || The TV Placed || Richard McAllister |- | 2005 || Fantastic Four || Reed Richards |- | 2004 || King Arthur || Lancelot |- | 2004 || Century City (TV series) || Lukas Gold |- | 2003 || This Girl's Life || Daniel |- | 2003 || Hornblower: Duty (TV series) || Commander Horatio Hornblower |- | 2003 || Hornblower: Loyalty (TV series) || Commander Horatio Hornblower |- | 2002 || The Forsyte Saga (TV) || Phillip Bosinney |- | 2002 || The Gathering || Dan Blakeley |- | 2002 || Shooters || Freddy Guns |- | 2001 || Black Hawk Down || Lt. John Beales |- | 2001 || Hornblower: Retribution (TV series) || 3rd Lt. Horatio Hornblower |- | 2001 || Hornblower: Mutiny (TV series) || 3rd Lt. Horatio Hornblower |- | 2001 || Happy Now || Sgt Max Bracchi |- | 2001 || Very Annie Mary || Hob |- | 2001 || Another Life || Freddy Bywaters |- | 2000 || 102 Dalmatians || Kevin Shepherd |- | 2000 || The Miracle Maker (TV) || Jesus (voice) |- | 1999 || Solomon & Gaenor || Solomon Levinsky |- | 1999 || Great Expectations (TV) || Pip |- | 1999 || Hornblower: The Frogs and the Lobsters (TV series) || Lt. Horatio Hornblower |- | 1999 || Hornblower: The Duchess and the Devil (TV series) || Acting Lt. Horatio Hornblower |- | 1999 || Warriors (TV) || Lt. John Feeley |- | 1998 || Hornblower: The Examination For Lieutenant (TV series) || Acting Lt. Horatio Hornblower |- | 1998 || Hornblower: The Even Chance (TV series) || Midshipman Horatio Hornblower |- | 1997 || Titanic || 5th Officer Lowe |- | 1997 || Wilde || John Gray |- | 1996 || Poldark (TV) || Jeremy Poldark |- | 1974 || Pobol y Cwm (TV series) || Gareth Wyn Harries (1987–1994) |}