Cowell has boarded "A Day in the Life" via his SyCo production company, reported Deadline.
The move marks Cowell's second feature length film project, after previously working on One Direction's concert documentary movie, "This Is Us", in 2013.
"A Life in the Day" will detail the story of Brian Epstein, who discovered the Fab Four during an appearance at the Cavern Club in Liverpool, England in 1961, and helped to turn them into global superstars before he died from a drug overdose in 1967, aged 32.
"Unbroken" star Jack O'Connell emerged as a frontrunner to portray Lennon in October last year, opposite Nicholas Hoult as Epstein, although casting details have yet to be made official.
It is also not known who will direct, but "Mandela: Long Walk to Freedom" filmmaker Justin Chadwick was linked to the job last year.
Rumours about Epstein and Lennon's relationship previously inspired the 1991 film "The Hours and Times".