Barrett lost to 2004 Athens Olympics silver medalist Amir Khan via a TKO in 2006; after which, he went on to fight for the British featherweight title in 2007.

Barrett is an English Superfeatherweight Champion, beating Femi Fehintola in the third round of their fight.

He is also an International Masters Lightweight Champion, winning in the first round against Mark Alexander.

He challenged for the WBU Lightweight World Title in 2009, but lost on points against Willie Limond.

On 7 December 2013 in Neuwied, Germany, Barrett was given a chance to avenge his loss in the Masters to Geoffrey Munika and in doing so took the vacant WBU Welterweight World Title with a 3rd-round TKO.