Thomas Frank’s side fell behind Antonio Rudiger’s stunner but Eriksen’s strike sandwiched between two from Vitaly Janelt sent the visitors into dreamland at Stamford Bridge, before substitute Yoane Wissa does not complete the beating late.
The 4-1 win lifts Brentford to 33 points and surely secures their Premier League status, 11 points clear of falling 14th.
Ivan Toney wasted two early chances for the visitors as Edouard Mendy got off to an unusually shaky start in Chelsea’s goal, but the home side gradually progressed through the game and were ahead at the break.
It took them just three minutes of the second half to find a breakthrough as Rudiger let the 35 yards fly and his effort fly off the post, giving David Raya no chance.
It caused wild celebrations but Stamford Bridge was silenced within two minutes as Janelt swept Bryan Mbeumo’s layoff into the top corner and on the hour mark a remarkable turnaround was complete.
First, Mbuemo ran down the left on the counterattack and as N’Golo Kante was dragged into cover, fed Eriksen through the middle to finish ahead of Mendy.
Then Toney slipped Janelt and from a tight angle the German lifted the Blues keeper superbly to give the Bees a break.
Kai Havertz missed two great chances to give Chelsea late hope before Wissa came off the bench to put them out of their misery with three minutes remaining.