Xavier was born in Victoria and grew up in Adelaide, South Australia. He graduated from Rostrevor College in 2001. Despite completing his studies at Rostrevor College, he undertook final year drama at Christian Brothers College, where his father taught English, due to a timetable clash. This notwithstanding, he played the part of Tom Snout in Rostrevor College's production of William Shakespeare's A Midsummer Night's Dream as well as playing the part of Belvile in CBC's production of Aphra Behn's The Rover (The Banished Cavaliers). He attended Flinders University Drama Centre in 2005 where he played Hamlet in the graduate production. During his time at university he was the lead singer of Adelaide band, Hyatus (formerly Degrees of Freedom). Samuel was recruited into the band by its bass player, Kelstar, who performed with him in the Banished Cavaliers. Samuel ultimately left Hyatus to pursue his film career. Samuel has also made theatre appearances in Osama the Hero, for which his performance was well-received by the Sydney Morning Herald. He has appeared in leading roles in the feature films September and Newcastle, and confirmed in July 2009 that he had been cast to play Riley Biers in Eclipse, the third movie in the Twilight film franchise.