On 14 November 2020, Brook moved back down to the welterweight division and attempted to become a two-time welterweight champion when he faced undefeated Terence Crawford in Paradise, Nevada for his WBO world title. In the fourth round, Crawford caught Brook with a right hand, and the referee administered a standing count to the latter. The fight continued, but Crawford quickly landed a flurry of shots which prompted the referee to step in and halt the contest, making Crawford the winner by fourth-round technical knockout.