An angled cross from midfielder Callum McGregor was met by right back Mikael Lustig, who sent a diving header past Aberdeen goalkeeper Joe Lewis.
The visitors doubled their lead 13 minutes after the interval as McGregor's outswinging corner was met by a powerful header from defender Jozo Simunovic, who also scored the winner against Kilmarnock last weekend.
Striker Odsonne Edouard added a third goal shortly before the final whistle to extend Celtic's unbeaten run to 11 games in all competitions since Lennon took charge as a caretaker manager following Brendan Rodgers's departure for Leicester City.
Celtic, the League Cup winners, could complete a third successive domestic treble when they meet Hearts in the Scottish Cup final on May 25.
(Reporting by Hardik Vyas in Bengaluru, editing by Ed Osmond)
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