LacPatrick is the second largest milk processor in Northern Ireland, behind Dale Farm.
The investment means its Artigarvan plant - formerly part of Town of Monaghan Co-Op - will increase capacity to 2.5 million litres of milk per day.
It will also underpin the future of more than 1,000 family farms that supply milk to the creamery.
The money will be used to build an evaporation tower at Artigarvan.
The company is expanding to meet demand in Europe, the Middle East, Africa and Asia.
The expansion will mean 15 new jobs, whilst up to 150 construction workers will be involved in building it.
Work has begun already and is due for completion in April 2017.
The company, LacPatrick, was formed when two creameries merged in July.  They were formerly Ballyrashane Co-Op, Coleraine, and Town of Monaghan Co-Op.
The LacPatrick Group has announced a £30m investment at its milk powder processing plant in County Tyrone.