Offshore wind and wave power are expected to offer viable alternatives to fossil fuels in the future. We assessed the predictability of available global offshore wind and wave power for lead times of up to 9 days using a state-of-the-art wave model and a six-member multi-model ensemble of operational numerical weather predictions during the boreal summer and winter for the period 2008–2012. The results show that wave power is predictable over large areas of the global ocean with a prediction error of <20% at a lead time of 3 days. In the tropical ocean, wave power can be accurately predicted even 9 days in advance. The predictability of wind power was generally low compared to that of wave power. However, wind power can be predicted 5 days in advance with the lower ensemble spread in the Pacific trade wind zone.