Lennon struck a minute into injury time just when it looked as though Fabricio Coloccini's 59th-minute winner had handed the Magpies all three points.
However, just as they had done last Sunday at Sunderland, Alan Pardew's men conceded in stoppage time to let two points slip from their grasp.
Spurs would argue that they deserved at least a point after dominating for long periods, but they left it desperately late to get their reward.
Leon Best and Luka Modric both it the bar and the Magpies were indebted to goalkeeper Steve Harper for two fines saves.
Newcastle went into the game once again shorn of key players Andy Carroll, Cheik Tiote and Steven Taylor and with Alan Smith ruled out for the rest of the season with an ankle injury.
Spurs had lost on each of their previous four visits to St James' Park, but the two clubs have enjoyed contrasting fortunes since their last encounter on Tyneside.
The visitors started at a high tempo and lone striker Jermain Defoe whipped a third-minute shot across Harper's goal after keeper Carlo Cudicini, deputising for the injured Heurelho Gomes, sparked a lightning attack with an early throw to Lennon.
Defoe was to prove a thorn in the Newcastle side for much of the opening 45 minutes, although without troubling Harper unduly until the dying seconds of injury time.
Spurs dominated possession, but as the Magpies got men behind the ball, they struggled to break their hosts down.
Man-of-the moment Gareth Bale, who lined up at left-back with new signing Steven Pienaar taking over ahead of him, lasted just 11 minutes before limping off to be replaced by Tyneside old boy Sebastien Bassong, and that removed one potential problem for Pardew's men.
There were plenty of others, however, although the Newcastle boss will have been reasonably satisfied with the way those challenges were met by his players.
Indeed, they started to make an impression themselves and after Shola Ameobi had failed to hit the target with two half-chances, they almost took the lead with 28 minutes gone.
Jose Enrique, who was largely occupied by Lennon, got forward well to send an inviting cross to the far post, where Best slid in to divert the ball on to the crossbar.
Spurs finished the half with a flurry, and almost went in front in injury time when they put together their best move of the half.
Rafael van der Vaart flicked Pienaar's pass into the path of Defoe, who seemed certain to score before Harper spread himself to make a vital block.
Newcastle returned in determined mood with Best proving a handful in the opening minutes of the second half, heading wide from a Jonas Gutierrez cross and seeing a shot blocked as he caused problems on the edge of the box.
But as the home side pushed men forward, the visitors started to exploit the space they left behind, although Pienaar in particular was unable to make the most of several promising openings.
However, it was the home side who took the lead in stunning fashion with 59 minutes gone when Coloccini controlled Danny Guthrie's cross on his chest before smashing a shot past Cudicini.
Tottenham would have been level within six minutes had it not been for another crucial intervention by Harper, who turned Lennon's well-struck shot around the post with the visitors responding.
Harry Redknapp sent on striker Peter Crouch for midfielder Jermaine Jenas with 19 minutes remaining, but Newcastle could have been 2-0 up within seconds when Joey Barton split the Spurs defence and substitute Peter Lovenkrands saw his first-time shot blocked by Cudicini.
Harper had his crossbar to thank for denying Luka Modric a 76th-minute equaliser with a fine right-foot drive, but substitute Nile Ranger wasted a glorious opportunity to secure victory in the final minute of normal time.
The miss proved costly in injury time when Lennon cut inside and blasted a right-foot shot past Harper to snatch a point.