Global loads acting on high-speed wave-piercing catamarans are investigated using computational fluid dynamics (CFD). Catamaran vessels are subjected to load cases that are not present on mono-hull vessels, such as transverse bending moment, pitch connecting moment and splitting force. As the speed and size of a catamaran increases the severity of loads rises with slam induced effects. Full-scale CFD simulation is undertaken to investigate the pressure distributions and resultant global loads acting on the 98 m INCAT wave-piercer catamaran HSV2 Swift, validated against sea trial tests. Rigid body dynamics are then applied to estimate the internal loads at different sections of the vessel based on the relative hydrodynamic and inertial force distributions. The estimated global loads are then checked according to DNV GL rules by comparing "design load limits". Global loads are estimated for the 98 m INCAT HSV2 Swift catamaran in headseas at a forward speed of 20 knots. Splitting forces are found to have a longitudinal distribution along the catamaran hull, which causes prying moments. Peak values for LBM are examined relative to corresponding instantaneous wave height prior to the slam event. In addition, it is found that pitch acceleration has a linear correlation with LBM slam loads.