A high mound composite seawall, which has a permeable front wall with a dissipation chamber on the superstructure, was newly developed as a revetment for reclaimed land. Several studies have focused on the hydraulic characteristics of high mound seawall; however sufficient examination has not been carried out on the oblique wave conditions. Threedimensional hydraulic model experiments were conducted to investigate the wave force characteristics and wave overtopping characteristics under oblique wave conditions. Based on the phase difference of impulsive wave force acting on superstructure, wave force reduction coefficients for oblique waves were proposed. Furthermore, influence of incident wave angle on wave overtopping rate and wave run-up height were studied.