Carvell made his Super League début for the Leeds Rhinos in 1997's Super League II as a 16-year-old against the Sheffield Eagles on Friday 22 August 1997. After a successful loan spell at the newly formed Gateshead Thunder in 1999, he signed for Hull F.C. in 2000 where he developed into one of the top s in the country, helping Hull F.C. to win the 2005 Challenge Cup Final. Hull F.C. reached the 2006 Super League Grand final to be contested against St Helens, and Carvell played as a in his side's 4-26 loss. In 2000, Carvell made his international début when he represented Wales in the 2000 Rugby League World Cup. Garreth represented Great Britain in 2006 in the 2006 Tri-Nations competition held in Australia. He also helped Hull F.C. reach the 2008 Challenge Cup Final. After signing a deal that would keep Carvell at Hull F.C. for the next 3-years he made a controversial U-turn and made the move to Warrington Wolves after a fee was paid. Carvell played for Warrington Wolves in the 2009 challenge cup final victory over Huddersfield Giants, 2010 Challenge Cup Final victory over Leeds Rhinos. and the 2012 challenge cup final victory again over Leeds Rhinos. He also featured in the 2012 and 2013 Grand final defeats. Garreth Carvell won caps for Wales while at Leeds 2000 1-caps + 2-caps, and won caps for Great Britain while at Hull F.C. in 2006 against New Zealand. He was named in the England training squad for the 2008 Rugby League World Cup. He played in the 2010 Challenge Cup Final victory over the Leeds Rhinos at Wembley Stadium. He was also named in England's 24-man 2011 Four Nations squad. He appeared off the bench against New Zealand at the KC Stadium, Hull, and in the final against Australia at Elland Road, Leeds. He played in the 2012 Challenge Cup Final victory over the Leeds Rhinos at Wembley Stadium. He played in the 2013 Super League Grand Final defeat by the Wigan Warriors at Old Trafford. In September 2014, Garreth was again called up to play for Wales in the 2014 European Cup. This was the first time that Garreth played for Wales in 14 years. But, unfortunately, he had to withdraw before the tournament due to an injury but he didn't completely leave the side as he took up an assistant coaching role. Midway through the 2013 season the Bradford Bulls announced that they had signed Carvell for the 2014 and 2015 seasons by signing him on a 2 Year Deal. Carvell featured in the pre-season game against Hull FC. However, in the week leading up to the first Super League game the Bulls went into administration and Carvell made the switch to former club Hull F.C. on a 1-year deal. He then moved to the Castleford Tigers before finishing his career with a brief spell at Featherstone Rovers in the Championship making his début for Featherstone Rovers on Sunday 26 April 2015.
