Fonterra said its chief financial officer, Jonathan Mason, would retire in the next six months.
The cooperative's chief executive Theo Spierings said Mason had always indicated that Fonterra would be his last full-time role.
"Jonathan joined Fonterra in the midst of the global financial crisis in 2009 and, under his leadership, ensured the co-operative's financial position was strengthened through those difficult times," Spierings said in a statement.
Mason also played a leading role in the launch of Trading Among Farmers share trading schme, which "significantly improved" Fonterra's capital structure.
Spierings said Mason had agreed to stay through to the end of the financial year while Fonterra identified a successor.