Neal Maupay fired the Bees into a deserved half-time lead in north London before Spurs raced ahead via goals from Destiny Udogie, Brennan Johnson and Richarlison after the break. Ivan Toney cut the deficit to set up a nervy finish but the hosts held on to claim a valuable win.
Despite the presence of James Maddison back in their starting line-up, Spurs lacked any invention going forward from the word go as Brentford's sturdy backline allowed them to wait patiently before launching counters at the hosts' high line.
A warning shot via Mads Roerslev's offside goal was not heeded by Tottenham and the visitors led after 15 minutes when Toney was played in behind. Guglielmo Vicario parried the striker's shot back into the danger area and Maupay beat Cristian Romero to it to break the deadlock.
Spurs shot into life briefly, with Timo Werner and Richarlison going close, but their confidence drained away as Brentford turned the screw - Ethan Pinnock stabbing a backheel a yard wide on 38 minutes before a Toney header was saved.
They were made to rue not extending their lead minutes after the restart when Ange Postecoglou's double change, introducing Pierre-Emile Hojbjerg and Johnson, paid off with a revitalised Spurs launching into the lead.
First it was Udogie who bombed into the box before making the most of a kind deflection to level the scores. Only 73 seconds later, Werner galloped down the left flank to cross for Johnson to tap home.
But a simple one-goal lead was not enough and Richarlison buried a third on 56 minutes after Tottenham again attacked with pace down the left, and Maddison's effort deflected into the Brazilian's path.
Toney fired millimetres wide with an effort from range before firing yards wide having sat the goalkeeper down in the box as Brentford reminded their hosts that the game was not yet over. On 67 minutes, the England striker finally made Spurs pay as he latched onto Udogie's poor backpass to score with Gareth Southgate watching on in the stands.
Tottenham kept a lid on their marauding runs forward as the clock ticked down, favouring playing the percentages and keeping the ball high up the pitch. Yet Brentford still had plenty of threat about them and Shandon Baptiste saw Vicario tip his side's best chance over the bar in stoppage time.