The Megamind actor was rumoured to have ended his relationship with Klein earlier this month, though no reason was given for the decision.
A source close to Hill has since confirmed the split to US Weekly, telling the publication that the couple's hectic careers came between them.
"Jordan always seemed really happy and in love. I never heard a single complaint about their relationship. It was probably travelling [that caused the split]. She would always go where he was. Now that she has a stable job, she can't just pack up and leave," the insider explained.
Hill, who has recently visibly slimmed down, recently insisted that losing weight is important as he wants to lead a healthier lifestyle.
He has said that he would love to direct a film like actor-filmmaker Ben Affleck.
Watch Jonah Hill in the trailer for Moneyball below: