Premature failures in large offshore Wind Turbines are often attributed to bearing failure despite gearboxes being designed and developed using the best bearing design practices. Furthermore, as turbine size and rated power increase, bearings display an enhanced tendency to fail. Unscheduled bearing replacement at sea is a complex, costly, weather-dependent and time-consuming operation that results in high turbine downtimes. Market trends show an increase in turbine rated capacity and a noticeable shift towards deeper waters and far-off remote sites which further delays and complicates unscheduled maintenance activities and aggravates the cost penalties of idle turbines. Detecting an incipient bearing fault (diagnosis task) is therefore a major aspect to evaluate drivetrain and overall wind turbine reliability. Moreover, estimating the remaining useful life of bearings and predicting their operational state in the future (prognosis task) can achieve a breakthrough in optimising maintenance programs, improve wind farm operation and decrease wind turbine downtime which can bring about a significant cost reduction. The purpose of this work is to investigate the health monitoring and prognostics possibilities of drivetrain bearings in a floating spar-buoy offshore wind turbine. The drivetrain concept considered in this work is based on DTU’s 10-MW reference wind turbine. Specifically, this study targets the prognosis of four critical drivetrain bearings located in the main shaft and the high-speed shaft.