McGettigan is to become chief executive of Lifestyle Sports, a chain with more than 70 outlets in Ireland. It had a turnover of more than €170m (£115m), in February.
He had been a major player in the grocery sector on both sides of the Irish Sea. He joined Dunnes in May last year after quitting as chief executive for food retail at The Co-operative Group just three months after taking the post.
Before that he was tipped to be the next boss of the Musgrave group, where he had spent 12 years and had been responsible for expanding the SuperValu and Centra franchise chains across Ireland. Later, as head of Musgrave's UK operations, he oversaw the Budgens and Londis acquisitions.
His departure from Dunnes will be a setback for the family-owned chain, which is struggling against Tesco, Aldi and Lidl.