Pfizer is creating about 300 jobs at its manufacturing sites in Grange Castle in Co Dublin, Newbridge in Co Kildare and Ringaskiddy in Co Cork.
The US drugs company said it is investing about €300m in its Irish operations to support the further development of the three sites.
The project will be completed over the next two to three years.
Pfizer currently has 4,000 workers across six locations based in Cork, Dublin, and Kildare in Ireland.
Pfizer’s Irish sites manufacture medicines and vaccines in the areas of arthritis, inflammation, cancer, anti-infectives, haemophilia, pain and stroke.