A first-half brace from Charlie Ide put Brentford ahead, but a remarkable turnaround after the interval saw Port Vale pull level through Luke Rodgers and Leon Constantine.
Brentford then went ahead again through a Joe Keith penalty, only for Constantine to restore parity with his 26th goal of the season.
The final dramatic twist came when Darius Charles scored at the death to give the Bees their first win in 12 games.
Perhaps inspired by the watching Terry Butcher - who was paraded on the pitch ahead of kick-off after being named as the new Brentford manager this week - the Bees quickly discovered their sting.
Paul Brooker's first-minute corner found Adam Griffiths at the back post and the Australian headed back into the six-yard box for Ide to flick a header home from close range.
But Vale refused to feel sorry for themselves, threatening through Akpo Sodje before Rodgers, put through by an incisive Rhys Weston pass, forced Brentford goalkeeper Nathan Abbey to parry the ball behind.
Brentford continued to look the more dangerous of the two sides going forward and with half-time beckoning they doubled their advantage.
Cutting in from the left, Ide skipped past Vale defender George Pilkington before firing a deflected shot past Joe Anyon for his seventh goal of the season.
But the visitors hit back strongly after the break, Pilkington heading narrowly wide from a Paul Harsley free-kick before Rodgers clawed one back for Martin Foyle's men with a superb free-kick from just outside the area.
Suddenly Brentford were rattled, and Vale were not slow to capitalize.
Constantine bundled the ball in from close range after Brentford failed to deal with a Clayton Fortune cross.
In the 66th minute Brentford regained the lead through Keith's penalty, which was awarded after Vale defender Michael Walsh was deemed to have handled in the area.
But with seven minutes to go Constantine swooped again, turning in from close range after a drilled cross from substitute Ross Gardner.
A familiar tale of woe seemed to be developing for Brentford, but there to be one last throw of the dice for the Bees.
With two minutes to go, Anyon failed to clear a Brooker cross and Charles was on hand to volley home the loose ball and send Griffin Park into delirium.