Harry Kane scored a goal and lost the game in perhaps his final home appearance for Tottenham.
The England captain, who again has been linked with an offseason move away from Tottenham, curled home after an indirect free kick in the eighth minute only for Bryan Mbeumo to score twice and set up another goal in the second half for Brentford in its 3-1 win in the Premier League on Saturday.
Tottenham might now struggle to qualify for any European competition for next season, having come into the game in seventh place — the division's only qualifying spot for the third-tier Europa Conference League.
Brentford stayed in ninth place but is only one point behind Tottenham ahead of the teams' final games of the season next weekend.
Kane's 28th league goal this season was perhaps his best of the campaign as he picked out the top corner with a 25-meter shot after Dejan Kulusevski rolled the ball backward with the sole of his foot at a free kick. It put Kane eight goals behind the league's top scorer, Erling Haaland.
Kane will be 30 years old by the time next season starts. With only one year left on his contract, he and Tottenham might decide this summer is the time to part ways to give the club a chance to get some money for its star player and for him to get a better opportunity for trophies.
“Speculation is speculation,” said interim Tottenham manager Ryan Mason, whose latest short-term stint in charge is likely to end after the trip to Leeds on May 28.
“We do have an important game against Leeds and there will be conversations. There are massive decisions to make but we can't look too far ahead. That's after the last game of the season and those conversations will definitely happen.”
Kane was joined by the rest of the squad in coming back out onto the field at Tottenham Hotspur Stadium for the end-of-season lap of appreciation, when he was also awarded the club's player of the season award from fans.
By then, the majority of home supporters had left, with Tottenham having slipped to a fifth loss in its last seven games.
Mbeumo cut in from the left for both of his goals, in the 50th and 62nd minutes, and then led a counterattack before setting up Yoane Wissa for a composed finish to seal victory for Brentford in the 88th.
Brentford was without Ivan Toney, who was handed an eight-month suspension on Wednesday for breaching betting regulations.
Brentford hosts Manchester City in its last match.