Brook was returning to 147lbs after losing to Gennady Golovkin at middleweight in his last bout, but he was outlasted by Spence in front of his home crowd as the American took his unbeaten record to 22 fights.
There was little to separate the two for much of the contest as both fighters stood toe to toe, with Brook perhaps narrowly in front heading into the second half of the bout.
However, as was the case against Golovkin, a swollen eye started to affect the Englishman as the fight wore on, and Spence was the one who grew into it and began to look stronger towards the latter stages.
Brook seriously faded in the ninth round and looked to be on the brink of defeat a round later when he was knocked down, but he somehow fought his way back and was arguably on top when the bell went.
The left eye was clearly having a growing impact on him, though, and he was eventually forced to take a knee in the 11th round while under pressure from Spence.
Brook looked eager to fight on beyond the count, but he failed to get back to his feet in time and the referee ended the contest as Spence claimed the welterweight title having passed the most difficult test of his career to date.