Dewey joins Ulster from Edinburgh where he has played since the 2004-05 season having previously played for Heriot's and represented Scotland at under-18, under-19 and under-21 levels as well as playing 7s for Scotland.

Dewey was the joint top try-scorer in BT Premiership Division One in season 2004-2005 with 16 tries for Heriot’s and made four appearances (including two starts) for Edinburgh before accepting a contract with the professional team ahead of season 2005-2006. He was a key member of the Scotland squad during the 2004 IRB Under 21 World Championship in Scotland.

Dewey travelled to South Africa with the Scottish squad on the 2006 summer tour, but did not play in either Test match but has since been involved in Scotland's Six Nations campaign this season and scored a try against England at Twickenham in the final moments of the game.