Collis, born in Campbelltown, New South Wales, Australia, started playing rugby league with Campbelltown Warriors and played for the Australian Schoolboys Team in 2003. Collis made his debut for Wests Tigers at the age of 18, making just one appearance in both the 2003 and 2004 seasons. He went on to make six appearances the following year and by 2006 he was a regular starter in the centres.
Collis went on to play every game of the 2006 and 2007 seasons; scoring nine and six tries respectively. He also earned a place in the New South Wales City Origin team for 2007.
The young centre’s next two seasons at Tigers were plagued by injury. During a training session with the Tigers squad, Collis was participating in a wrestling drill with team mate Dene Halatau. Halatau fell and landed on Collis, breaking his arm and sidelining the centre for six weeks of the 2009 season. In July 2009 it was announced that Collis would sign for Cronulla-Sutherland Sharks on a two year deal, Collis played his final game for Wests Tigers on the 4th September 2009.
Collis made his debut for Cronulla on 29th March 2010 against South Sydney Rabbitohs. He injured his ankle in a tackle very early in the game and was ruled out for three games. During his first season at Cronulla-Sutherland Sharks, he made 19 appearances and scored 7 tries. He played his 100th NRL game against Canberra Raiders in round one of the 2011 season, which saw Cronulla defeated 40-12.
Dean only featured in four more games during the 2011 season, none of which were won by Cronulla leaving the team finishing second from bottom with just 16 points.
On September 16th it was announced that Collis would sign a three year deal with Wakefield Trinity Wildcats and in turn leave Australia and the Telstra Premiership. He became new Wakefield coach Richard Agar’s first signing of the campaign.
|08/02/2015||15:30||Super League||Castleford Tigers||22 - 24||Wakefield Trinity|
|15/02/2015||15:00||Super League||Wakefield Trinity||44 - 24||Hull KR|
|01/03/2015||15:00||Super League||Widnes Vikings||58 - 16||Wakefield Trinity|
|06/03/2015||20:00||Super League||Wakefield Trinity||16 - 20||St Helens|
|15/03/2015||15:00||Super League||Salford Red Devils||24 - 18||Wakefield Trinity|
|22/03/2015||15:00||Super League||Wakefield Trinity||14 - 44||Huddersfield Giants|
|27/03/2015||20:00||Super League||Wigan Warriors||52 - 10||Wakefield Trinity|
|02/04/2015||20:00||Super League||Wakefield Trinity||4 - 40||Catalan Dragons|
|17/05/2015||14:15||Challenge Cup||Wakefield Trinity||30 - 36||Leigh Centurions|
|24/05/2015||15:00||Super League||Wakefield Trinity||18 - 30||Widnes Vikings|
|31/05/2015||17:30||Super League||Castleford Tigers||56 - 16||Wakefield Trinity|