The Bhoys avenged last month's Camp Nou defeat to the Spaniards, with goals from Victor Wanyama and Tony Watt sealing victory before a late Lionel Messi consolation.
And the Northern Irishman has admitted it is hard to believe he will enjoy a better night for the rest of his managerial career.
"It's one of the greatest nights in the club's recent history," Lennon told reporters.
"It was very poignant to be playing Barcelona on our 125th anniversary and we did so decimated by injuries. It's up there with anything I've done in my life, not just in football.
"As a manager I don't know if I'll top that - I hope I do."
The win leaves Celtic just two points behind the Group G leaders with two games left to play, and Lennon insists his side now stand a real chance of progressing through to the next round.
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"The problem now will be the expectation level. There's still a lot of work to do. But that's for the future."
The 41-year-old also singled out England international Fraser Forster for praise before going on to highlight the gulf in quality between the two squads.
He added: "You need your goalkeeper to be fantastic to beat Barcelona. You need luck as well and Barcelona hit the bar and the post.
"But the difference between me and Tito Vilanova [Barca's coach] is that he can bring on Cesc Fabregas and David Villa, I bring on Tony Watt, an 18-year-old signed for £50,000 from a club called Airdrie.
"When I took the job on, I said I wanted to bring the thunder back and I've never seen an atmosphere like I did tonight."