The Celtic manager harboured ambitions of a career caring for animals as a young boy in Lurgan, Northern Ireland.
He had to give up on his ambition after flunking his biology exams at school.
The Parkhead boss told of his secret ambition during an online question and answer session with fans hosted by Celtic sponsors Magners.
One supporter asked Lennon: “If you didn’t succeed as a footballer what career do you think you’d have now?”
The former midfielder replied: “I wanted to be a vet. Though my biology studies didn’t go quite as well as planned.”
The Northern Irishman said he became hooked on football after joining a supporters club team in Lurgan.
He added: “I played boys club football for the Celtic Supporters Club in my home town.”