Goalkeeper Jens Lehmann was at fault as below-par Arsenal twice surrendered the lead to draw at Panathinaikos.
Freddie Ljungberg converted Jose Antonio Reyes' pass but Lehmann was caught out of goal allowing Ezequiel Gonzalez to superbly lob an equaliser.
Thierry Henry restored Arsenal's lead but Lehmann was stranded from a corner as substitute Emmanuel Olisadebe headed the Greek team level again.
Greek keeper Kostas Chalkias made two brilliant late saves to ensure a draw.
Arsenal went into the game with Cesc Fabregas making his first start in the Champions League in the absence of Patrick Vieira.
And the Arsenal skipper's presence in midfield was sorely missed as the Gunners surrendered possession far more than normal.
Arsene Wenger's side rarely showed the craft and guile that so often characterises their play in the Premiership and deserved no more than a point.
Panathinaikos, playing in front of their passionate supporters, created the early opportunities.
The impressive Angelos Basinas shot narrowly wide with his first attempt and then forced Lehmann into a good save with a thunderous strike from long range.
But when Arsenal finally started to impose themselves they soon carved open the Greek defence with Reyes' sublime threaded pass - and Ljungberg made no mistake from seven yards.
Panathinaikos continued to press forward and Gonzalez made a superb late run into the Gunners box but could not direct his header on target while Basinas threatened again from long range just after the half hour.
Sotiris Kirgiakos headed wide and Basinas shot narrowly over Lehmann's bar with a vicious free-kick as the home team searched for an equaliser.
Panathinaikos continued to show greater urgency and desire after half-time - and they were finally rewarded for their endeavour with a well-deserved equaliser.
Campbell seemed to have a long ball upfield covered but Lehmann chose to surge from his goal and head clear.
Gonzalez punished the German keeper with a brilliant opportunist strike, looping the ball over Lehmann from all of 35 yards wide on the right.
Arsenal took the lead again after a rare error from Basinas led to a lightning-fast break.
Reyes, Robert Pires and Cole manoeuvred the ball up field at blistering pace and Henry, quiet all evening, slid in to restore Arsenal's lead.
Arsenal seemed to be coasting but another poor piece of defending allowed substitute Olisadebe to head Panathinaikos' second equaliser of the evening.
Olisadebe was poorly marked, while Lehmann came from his goal but was caught in no-man's land.
The visitors seemed certain to take the lead for a third time with minutes left but Chalkias made a brilliant double save from Reyes and Pires.
Panathinaikos: Chalkias, Morris, Goumas, Gonzalez (Sapanis 90),
Kirgiakos, Konstantinou (Olisadebe 64), Basinas,
Mitu (Epalle 76), Vyntra, Skacel, Konstantinidis.
Subs Not Used: Galinovic, Henriksen, Kotsolis, Maric.
Booked: Goumas, Skacel, Vyntra.
Goals: Gonzalez 65, Olisadebe 81.
Arsenal: Lehmann, Lauren, Toure, Campbell, Cole, Ljungberg,
Edu, Fabregas, Pires, Reyes, Henry.
Subs Not Used: Taylor, Van Persie, Flamini, Cygan, Senderos,
Goals: Ljungberg 17, Henry 74.
Ref: Valentin Ivanov (Russia).