[3] Born in Isleworth, London, Dobson began his career as a forward in the youth system at Brentford at the age of 9 and also played for Sunday club West Middlesex Colts.

[3][6] Dobson finally made his senior debut as a 71st-minute substitute for Andy Scott during a 0–0 Second Division draw with Swansea City on 19 August 2000.

[7][9] Under new manager Steve Coppell, Dobson was Brentford's regular right back during the 2001–02 season,[10] in which the club narrowly missed out on automatic promotion,[11] before advancing to the 2002 Second Division play-off final, which ended in a 2–0 defeat to Stoke City.

[8] Despite being plagued by pelvic bruising during the season, which required painkillers,[12] Dobson made 46 appearances and scored one goal, which came in a 3–2 FA Cup second round defeat to Scunthorpe United on 8 December 2001.

[10] After the play-off final defeat at the end of the 2001–02 season, financial concerns led new manager Wally Downes to reduce the size of the Brentford squad and at the age of 21, Dobson was named as the new team captain.

[15] The Bees' slump continued into the 2003–04 season and Dobson's form suffered due to a niggling back injury,[3][16] but the appointment of Martin Allen as manager in March 2004 reinvigorated the team and the club narrowly pulled off "The Great Escape" from relegation to the Third Division.

[3][21][22] He won back his place upon his return in January 2005, but began to drift out of the starting lineup in February and a broken arm suffered in a match versus Stockport County on 2 April ended his season.