Teva Pharmaceutical is to create more than 165 new jobs over the next five years at its IVAX facility in Waterford.
The company, which is headquartered in Israel, is the world's largest manufacturer of low-cost generic medicines. IDA Ireland is backing its €65m investment.
The existing facility supplies Teva's respiratory products and also makes a range of treatments for the US market. The site is also the company's main research centre for respiratory products.
Teva says the investment will allow the Waterford operation to more than double both its inhaler and tablet manufacturing capacity.