Tottenham's huge summer spending spree failed to deliver an immediate return as Brentford produced a dominant performance to dismantle Roberto de Zerbi's side at the Gtech Community Stadium.
Spurs have invested around £237m in new players this summer, breaking their transfer record twice as they attempt to move on from consecutive 17th-place Premier League finishes.
Four new arrivals were handed starts in west London, with defenders Andy Robertson, Marcos Senesi and Jan Paul van Hecke joining £100m club-record signing Sandro Tonali in the starting line-up.
But despite all the investment, Tottenham found themselves two goals behind after just 33 minutes.
Keane Lewis-Potter opened the scoring in the 12th minute after Brentford's own record summer signing, Mamadou Sangare, picked out the unmarked full-back inside the penalty area.
Sangare was outstanding in midfield as the Bees took control of the contest, and their pressure eventually produced a deserved second goal.
Tottenham goalkeeper Antonin Kinsky initially kept out Mathias Jensen's effort, but Vitaly Janelt reacted quickest to convert the rebound and double Brentford's advantage.
While the hosts played with intensity and attacking purpose, Tottenham offered almost nothing going forward and failed to register a shot on target during the opening 45 minutes.
De Zerbi responded by making two changes at half-time, introducing £85m signing Mateus Fernandes and Rodrigo Bentancur in place of Conor Gallagher and Lucas Bergvall.
The changes did little to alter the direction of the match.
Brentford added a third when Sangare's shot was saved and the loose ball fell kindly for Michael Kayode, who made no mistake with the opportunity.
Things almost became even worse for Spurs when Bentancur brought down Kevin Schade and referee Michael Oliver awarded Brentford a penalty.
Igor Thiago sent Kinsky the wrong way from the spot, but his effort struck the post and bounced to safety.
The miss ultimately mattered little as Brentford comfortably saw out a convincing victory over a Tottenham side that showed few signs of improvement despite their expensive summer rebuild.
Tottenham failed to win a single Premier League match after falling behind last season, and the same weakness immediately resurfaced against Brentford.
This was intended to mark the beginning of a new chapter under De Zerbi after two successive 17th-place finishes. Instead, many of the problems that plagued Spurs last season were again painfully evident.
Brentford found it far too easy to expose Tottenham's defence.
Lewis-Potter was completely unmarked for the opening goal, Richarlison surrendered possession in the build-up to the second and the defensive structure collapsed again when Kayode scored the third.
Tottenham continue to pursue attacking reinforcements and are in talks over possible moves for Manchester City forwards Savinho and Omar Marmoush.
However, their performance at Brentford suggested defensive additions may be an even greater priority.
Injured captain Micky van de Ven could only watch from the bench as 20-year-old Archie Gray became Tottenham's youngest-ever captain.
It proved a difficult afternoon for Gray, who was eventually substituted late in the match and handed the captain's armband to James Maddison, who missed much of last season through injury.
By that stage, many of the travelling Tottenham supporters had already headed for the exits as the home fans celebrated an emphatic start to the new campaign.
After such significant investment during the transfer window, De Zerbi will know performances like this will quickly increase the pressure on his rebuilt squad.
While Tottenham struggled, Brentford delivered almost everything manager Keith Andrews could have wanted from his team's opening Premier League performance.
Expectations have increased after the Bees finished ninth last season and narrowly missed out on European qualification on goal difference, but they looked more than capable of dealing with that added pressure.
Sangare was at the centre of their impressive display.
The Mali international, signed from Lens, provided the assist for Lewis-Potter's opener and continually caused problems with his energy and creativity in midfield.
His contribution included two key passes and a shot on target, while his overall performance earned him a standing ovation when he was substituted in the 76th minute.
Brentford were organised, energetic and aggressive throughout, completely outworking their London rivals.
In fact, the three-goal margin could easily have been greater.
Captain Nathan Collins headed an excellent opportunity wide while the score was still goalless as Brentford registered four attempts within the opening eight minutes.
Dango Ouattara later wasted another good opportunity with the score at 1-0, while Thiago's missed penalty denied the hosts the chance to make the result even more emphatic.
The final statistics underlined Brentford's superiority, with the Bees producing 26 attempts compared with Tottenham's nine.
After narrowly missing out on Europe last season, Andrews' side have started the new campaign with a statement victory and will look to maintain that momentum when they travel to face Leeds United next.
