Nowadays, offshore renewable energy is seen more and more as an attractive alternative to onshore energy thanks to less space limitations and usually better weather conditions. However, the higher costs in installation and maintenance demand a continuous search for higher conversion efficiency in order to achieve an economically viable electricity generation. In this line, the co-location of wind and wave power sources might serve to reduce the generation power variability and also to take advantage of using the same infrastructure and implementation area. Several studies have been carried out mainly focused on determining possible zones of implantation or developing new co-location concepts. However, the optimization and control of these new offshore energy conversion systems have not been extensively studied in the literature. This article presents a new optimal control strategy for co-located wind and wave farms in order to fulfill the operation and integration requirements demanded by power system operators. The proposed control scheme is evaluated in several realistic scenarios. The obtained results show that with adequate control strategies, it is possible to increase the electricity production of co-located wind-wave farms satisfying the frequency requirements of the network, even in adverse events, and also to increase the total power reserve of the system.