The frontman has been taken to the Bees as a replacement for injured striker Nathan Elder and he will be in the squad to face Barnet on Tuesday night.
Despite a number of lower league outings at Wrexham, Brighton, Colchester and most recently Walsall, Williams has never had the chance to play first team football at Villa Park.
At the age of 21, Williams must now prove his worth, as his status as a hot prospect is fading.
The spell at Brentford may just be what he needs to earn a move to a League One or Two side, but you never know, he may just impress sufficiently to finally earn a first team chance at Villa.