A defiant Ange Postecoglou believes Tottenham have enough to win trophies this campaign as he "always wins things in his second year". (More Football News)
Gabriel Magalhaes scored the decisive goal for the Gunners in the 64th minute, profiting from some slack defending on a corner as he thumped in the winner.
Spurs had the better chances, especially in the first half, finishing the game with 15 shots overall, more than double what Arsenal managed (seven).
The hosts also dominated possession with 63.7% and entered the final third 62 times, but as they did against Leicester City on the opening day, they struggled to take their chances.
Asked if he thought his team had enough to challenge for silverware this season, Postecoglou told Sky Sports: "I don't usually win things, I always win things in my second year," he told Sky Sports. "Nothing's changed. I don't say things unless I believe it."
Postecoglou has failed to beat Arsenal in three Premier League attempts and was left to lament their lack of a clinical edge after the match.
"It's very disappointing in a big game for us and our supporters. We didn't deliver so you have to take the pain from that," he added.
"It has been the story of our season so far, we played in their half and created chances, but we lack a bit of belief in the final third. That's what we need to fix. It was always going to be decided in moments, and they capitalised on theirs.
"It's me who has to give the guys the way forward. It's not for a lack of trying by the lads, we are just going through this early part of the season where we are playing well but not getting rewards for it.
"We handled set-pieces pretty well, but we switched off for one and paid the price."
Son Heung-min made his 19th Premier League appearance in the North London derby, with only Sol Campbell (22) playing in more among outfield players.
The Spurs captain struggled to make an impact though, worth just 0.04 expected goals (xG), and he echoed Postecoglou's frustrations.
"We dominated the game; the football was there, we just conceded from a set-piece again. We did it last season, and it is really frustrating," Son said.
"I am sure the fans are also very disappointed. We have to improve, 100%. It's a tough moment and we have to stick together.
"We are getting into the final third, but the players have to take the responsibility to score. It is the hardest part of football, making the right decision and being clinical.
"We will bounce back strong, there is a long way to go."
