Sampson started his career at Stanley Rangers before joining Castleford in 1986, and made his first team début in 1987.
Dean Sampson played right-prop, i.e. number 10, in Great Britain's 14-8 victory over Auckland on the 1992 Great Britain Lions tour of Australasia at Carlaw Park, Parnell, New Zealand on Wednesday 8 July 1992, and played left-prop, i.e. number 8, in Great Britain's 17-6 victory over Canterbury on the 1992 Great Britain Lions tour of Australasia at Rugby League Park/Addington Showgrounds, Christchurch on Wednesday 15 July 1992.
In the 1997 post season, Sampson was selected to play for Great Britain in the first match of the Super League Test series against Australia.
Dean Sampson won caps for England while at Castleford in the 1995 Rugby League World Cup against Fiji, South Africa (interchange/substitute), and Wales (interchange/substitute), and in 1999 against France (twice).
Dean Sampson was an interchange/substitute, i.e. number 15, (replacing Left-Prop Lee Crooks on 33-minutes) in Castleford's 12-28 defeat by Wigan in the 1992 Challenge Cup Final during the 1991–92 season at Wembley Stadium, London on Saturday 2 May 1992, in front of a crowd of 77,386.
Dean Sampson played as an interchange/substitute, i.e. number 15, (replacing Hooker Kevin Beardmore) in Castleford's 12-12 draw with Bradford Northern in the 1987 Yorkshire County Cup Final during the 1987–88 season at Headingley Rugby Stadium, Leeds on Saturday 17 October 1987, played as an interchange/substitute, i.e. number 15, (replacing Prop John Fifita) in the 2-11 defeat by Bradford Northern in the 1987 Yorkshire County Cup Final replay during the 1987–88 season at Elland Road, Leeds on Saturday 31 October 1987, played as an interchange/substitute, i.e. number 15, (replacing interchange/substitute David Roockley) in the 12-33 defeat by Leeds in the 1988 Yorkshire County Cup Final during the 1988–89 season at Elland Road, Leeds on Sunday 16 October 1988, and played prop, i.e. number 10, in the 11-8 victory over Wakefield Trinity in the 1990 Yorkshire County Cup Final during the 1990–91 season at Elland Road, Leeds on Sunday 23 September 1990.
Dean Sampson played as an interchange/substitute, i.e. number 15, (replacing Prop Martin Ketteridge on 74-minutes) in Castleford Tigers' 33-2 victory over Wigan in the 1993–94 Regal Trophy Final during the 1993–94 season at Headingley Rugby Stadium, Leeds on Saturday 22 January 1994.
Dean Sampson came back in 2003 when Castleford went through an injury crisis, scoring on his comeback game against Warrington Wolves. He also played once more for Castleford in 2005 against Hull Dockers in the Challenge Cup. Overall Dean played 431 games for Castleford scoring 68 tries. With 431-appearances, Dean Sampson is joint second (along with Artie Atkinson) in Castleford's all-time appearance list behind John Joyner, who has 613-appearances. Dean was a real fans favourite for Castleford and his name was often chanted by the home fans.
After retirement, Sampson became the club's academy coach and won the Junior academy championship in 2004. He left the club in 2005 and moved to Hull Kingston Rovers and became the assistant coach there. He left Hull KR after a brief period and stayed out of the game for a while.
Sampson has rejoined Castleford for 2009's Super League XIV and was the club's academy coach once again.
Dean Sampson is a Tigers Hall Of Fame Inductee.
Dean is the son of rugby league player and coach Dave Sampson, the nephew of rugby league player Malcolm Sampson, and cousin of the sprinter Denise Ramsden, and rugby union and rugby league player Paul Sampson.