Paul Robinson's error allowed Robert Pires to equalise for Arsenal and prevented Tottenham beating their rivals for the first time in 13 games.
The England keeper dropped a cross and Pires coolly side-footed in to rescue a barely-deserved point for the Gunners.
Defender Ledley King had opened the scoring after he rose unmarked to convert Michael Carrick's free-kick.
Jermain Defoe also went close for Spurs, while Arsenal's Robin van Persie and Freddie Ljungberg threatened.
Substitutes Van Persie and Pires changed Arsenal's fortunes - they had looked to be heading for defeat at the hands of Spurs for the first time in six years.
Robinson was forced into a number of late stops - having been a bystander for much of the game - particularly from Dutchman Van Persie.
Spurs, too, had their chances, with a brilliant, mazy dribble and shot from Defoe being one of their best.
It was a rousing end to a passionate derby that had seemed as though it could end only one way - with Spurs as the victors.
Encouraged by the direct running of Mido, who galloped beyond Lauren early on to give warning of his superior pace, Spurs settled more quickly.
Aaron Lennon followed Mido's lead and enjoyed success when he ran at the Arsenal defence.
Yet Arsenal could have been first to penetrate the goal when Jose Antonio Reyes seemed to have left King in his wake.
But the England defender recovered to win possession with a superbly-timed challenge in the penalty area.
Shortly afterwards, King spirited into the area at the other end to emphatically demonstrate his ability to score goals as well as prevent them.
And once ahead, Spurs pushed on - Carrick's shot fizzing wide before a rising shot from Jermaine Jenas worried Lehmann.
Arsenal's passing continued in wayward fashion, more often finding the touchline than a team-mate.
And Spurs fans cheered their team's every successful pass, including a roar when manager Martin Jol precisely volleyed the ball back from the sidelines when it had gone out of play.
By contrast, Gunners coach Arsene Wenger may have been tempted to tuck the ball under his shirt and refuse to give it back.
It would, perhaps, have been the only way for Arsenal to retain possession in the first half.
And they were fortunate not to concede a second goal when Jenas mistimed the swing of his boot, swiping air rather than leather at the near post.
After the interval, Pires came on for the ineffective Matthieu Flamini.
It jarred Arsenal into life and Ljungberg latched on to Dennis Bergkamp's through-ball, but found Robinson equal to his low left-foot shot.
However, most of the action continued to take place in Arsenal's goal area - and in nasty fashion when Lehmann appeared to be hit by a missile from the crowd behind the goal.
But it was Robinson who would be involved in the most telling moment, when he spilled a cross and allowed Pires to slot the ball into an empty net.
Tottenham: Robinson, Stalteri, Dawson, King, Lee, Lennon (Reid 73), Jenas, Carrick, Tainio (Pedro Mendes 79), Mido, Defoe (Keane 82).
Subs Not Used: Cerny, Naybet.
Booked: Defoe, Dawson, Lee, Tainio.
Goals: King 17.
Arsenal: Lehmann, Lauren, Campbell, Toure, Clichy, Ljungberg (Van Persie 65), Flamini (Pires 45), Silva, Fabregas, Bergkamp, Reyes (Cygan 90).
Subs Not Used: Almunia, Eboue.
Booked: Silva, Flamini.
Goals: Pires 77.
Ref: S Bennett (Kent).