The aim of this study is to develop a new probabilistic approach to determine nominal values for tank sloshing loads in structural design of LNG FPSO (liquefied natural gas, floating production, storage, and offloading units). Details of the proposed procedure are presented in a flow chart showing the key subtasks. The applicability of the method is demonstrated using an example of a hypothetical LNG FPSO operating in a natural gas site off a hypothetical oceanic region. It is noted that the proposed method is still under development for determining reliable estimates of extreme sloshing induced impact loads. It is concluded that the developed method is useful for determining the sloshing design loads in ship-shaped offshore LNG installations in combination with virtual metocean data and operational conditions.