Abstract | Wind Turbines constitute a sustainable and effective solution for the production of energy using wind power. Offshore wind turbines especially are becoming of special interest. However, their design poses great challenges, since an offshore structure is subject to combined wind and wave dynamic loading that is characteristic of the site of installation. The purpose of this paper is to provide a case study of fatigue life assessment for the cross-section at mudline (foundation) of a standard offshore wind turbine with a monopile design, under a probabilistic framework and assuming the thickness of the examined cross-section as the design variable. Two potential sites of construction in the Aegean Sea of Greece were examined. A probabilistic approach was employed in order to determine the fatigue life based on anemological data at each of the two sites of interest. At its basis is an extensive Monte Carlo simulation of wind (velocity) and wave (height, period) characteristics. The results show the dependence of fatigue life on the local wind and wave conditions, the cross-section geometry (i.e. the thickness of the foundation’s pile) and the welded connection detail. All in all, the more benign conditions in the Aegean allow simpler connection details and smaller thickness of foundation pile’s cross-section to still have acceptable performance.