Three goals came in 10 second-half minutes with Ollie Watkins eventually striking the winner, which ended Preston’s unbeaten home record this season.
Defeat also extended Preston’s winless run to four league games and the have now conceded 10 goals in their last four matches, having conceded just four in their first 10.
Preston began the better of the two sides and Jordan Hugill created the first chance of the game after eight minutes by out-muscling Andreas Bjelland only for Tom Barkhuizen to slice wide from the edge of the area.
And the pair combined again five minutes later as Hugill, making his 100th Preston appearance, latched on to Barkhuizen’s through-ball but curled wide from 18 yards.
But it was Brentford, who have now lost just one of their last 10 meetings with Preston, forcing the first save with Florian Jozefzoon, cutting in from the right and his low shot from 15 yards was tipped wide by Chris Maxwell.
And the visitors took the lead after 25 minutes as Jozefzoon found space again and his powerful strike was parried by Maxwell but straight to Nico Yennaris who nodded in from eight yards.
Preston almost struck back instantly but Sean Maguire headed Daniel Johnson’s cross over from six yards.
Alex Neil’s side were on level terms after 41 minutes as Maguire picked up a Hugill flick-on and drove at the retreating Brentford defence before firing low into the corner from 15 yards.
The game was then delayed as Yennaris received significant medical treatment after seemingly being inadvertently caught by Hugill’s shoulder on the stroke of half-time, before being carried off to applause from both sets of fans.
Brentford were back in front after 56 minutes through substitute Romaine Sawyers, who was afforded time and space on the edge of the box after missing his first strike and his effort was deflected into the left-hand corner.
Barkhuizen tried to inject some life back into the hosts after 63 minutes as he surged into the area, but his strike was blocked before referee David Coote waved away penalty claims.
And Preston threatened again a minute later as Callum Robinson picked the ball up and fired just wide from 25 yards.
Their increased pressure told after 66 minutes as the ball dropped to Barkhuizen 20 yards out, who controlled the ball on his chest before lashing it in on the volley.
But just three minutes later Brentford had their winner. Jozefzoon broke in behind and slid a simple ball across the area where Watkins tapped in from six yards.