Gareth David-Lloyd began acting when he was in junior school, later joining both the Gwent Young People's Theatre and the Dolman Youth Theatre. He appeared in several stage productions across Wales while studying at Coleg Gwent, and later trained for the National Youth Theatre and the Rep College.
David-Lloyd made his screen debut in 2003, and later appeared in shows such as Casualty and The Bill. He first worked with Torchwood creator Russell T. Davies in the BBC drama Mine All Mine. He joined the Doctor Who spin-off, Torchwood, in 2006, appearing as Torchwood member Ianto Jones; his character's popularity was such that, when he was killed off during the third season finale in 2009, fans created a memorial wall near Cardiff Bay, where the show is shot.
David-Lloyd also fronts the prog metal band Blue Gillespie; they released their first EP in 2008; their debut LP, Synthesia, came out two years later.