Belgian firm OWA will be responsible for the maintenance of the balance of plant, including foundations and submarine cables. OWA is part of Deme's GeoSea vessels subsidiary.
German company EWE will service the onshore cables, two offshore transformer stations and an onshore transformer at Eemshaven. The contract will last five years, beginning in 2016.
Gemini is owned by Northland Power (60%), Siemens (20%), Van Oord (10%) and HVC (10%). It is located 85-kilometres off the Dutch coast.
The project will use Siemens' 4MW turbine with a 130-metre rotor, and monopile foundations.
Earlier this month, EPC contractor Van Oord installed the first of the 150 monopiles from its Aeolus vessel and the first substation has been put in place. Gemini is due online in 2017.