Eoin Tonge, the chief financial officer of Greencore, leaving the group to take on the same role at Marks and Spencer (M&S).
Mr Tonge has been with the convenience food company for 14 years.
He will step down following the group’s interim results in May.
A process to determine a successor is now underway.
Patrick Coveney, Greencore CEO, said: "He leaves with our gratitude for his enormous contribution to the group but he also has our very best wishes for the future. We have a strong finance team at Greencore and have already commenced a process to appoint a new chief financial officer."
Last month Greencore said its revenue increased 1.8pc to £367.8m (€435m) in the three months to 27 December.
On a pro forma basis, adjusting for acquisitions and site exits, revenue increased by 0.7pc, according to a trading update.