The company is expected to invest €100m in the manufacturing sites.
The company will produce nacelles and generators in Saint-Nazaire while blades will be produced in partnership with LM Wind Power in Cherbourg.
Alstom will select a new supplier which will set up a manufacturing workshop to develop towers.
The company intends to produce the Haliade 150, the first new generation 6 MW offshore wind turbine.
Each Haliade 150 will be equipped with 241ft blades and will be capable of supplying power to 5,000 homes.
