The outsourcer - best known to many for its problems providing security at the London 2012 Olympics - said Tim Weller, currently the chairman of its audit committee, will replace current chief financial officer Himanshu Raja when he steps down in October.
Weller, who is currently the chief financial officer of oil giant Petrofac, will step down from G4S' audit committee with immediate effect. He'll leave Petrofac in October, the oil giant said in a separate statement.
"Tim is a highly accomplished executive with extensive commercial and financial experience in global businesses. His experience and skill will be invaluable in leading our global finance team and supporting our broader transformation programme," said Ashley Almanza, the company's chief executive.
"It is greatly to our advantage that Tim arrives with an already deep understanding of G4S and our well established transformation programme."
G4S' shares hit a six-month high last week after pre-tax profits jumped in the six months to the end of June, from £80m in 2015 to £115m this year.
That came a few short months after G4S was unceremoniously dumped from the FTSE 100 thanks to poor share performance.