Ajax were ahead inside two minutes in the Group H clash, but Jorginho equalised from the penalty spot two minutes later.
By the 55th minute, though, Chelsea were 4-1 behind after Quincy Promes' header, Kepa Arrizabalaga's own goal and Donny van de Beek's fine strike.
Cesar Azpilicueta pulled one back just after the hour before Jorginho slotted another penalty, and both Daley Blind and Joel Veltman were sent off for the visitors.
In the 74th minute, 19-year-old substitute Reece James fired home the equaliser, and in the closing stages Azpilicueta had his apparent winner ruled out by the VAR:
Lampard, a Champions League winner himself as a player in 2011-12, said he had never seen a game like it, and he praised his experienced players for keeping their heads when the Blues were down, per MailOnline's Daniel Matthews:
"I have had some mad nights and some great nights. I don't think I've been involved in a game like that. For a performance like today you need characters and personalities. At 3-1 down at half-time, it's easy to turn it in.
"Even easier at 4-1 and give it up. But we never did. I keep saying it about the experienced players, the Jorginhos, cool head, driving the team, [Mateo] Kovacic, Willian, sure, but Azpilicueta, those players really pushed tonight, and I loved it."
The result leaves Group H tantalisingly poised after Valencia beat Lille 4-1.
Los Che, Ajax and Chelsea are all tied on seven points with two games of the group stage remaining:
Chelsea face Valencia at the Mestalla in three weeks before their final pool game at home to Lille.
The visit to Valencia could be crucial to whether the Blues qualify for the knockout rounds because the first tiebreaker if teams are level on points is head-to-head matches, not overall goal difference.
Chelsea were beaten 1-0 by the La Liga side at Stamford Bridge in the opening game of their European campaign this season.
Lampard's side are back in action on Saturday in the Premier League when they host Crystal Palace.