The 53-year-old is starring in the new movie Tinker, Tailor, Soldier, Spy but admitted being a single dad to his sons Gulliver, 14, and Charlie, 12, has been his most difficult role.
Oldman split from his third wife Donya Fiorentino in 2001 and he was awarded custody of their sons.
He said to Time Out magazine: 'Raising kids is the hardest thing I've done. Harder than anything.'
The actor took a break from movies when he became a single dad and he said: 'Yeah. You know, my life took a different direction. That was my story.'