Abstract In Part I, viscous effects on bottom hinged Oscillating Wave Surge Converters (OWSCs) were investigated numerically. In the present paper (Part II), the slamming on an OWSC is studied both experimentally and numerically. Numerical simulations are performed with the Volume of Fluid (VOF) approach for capturing the interface between air and water and the dynamic mesh method for modelling the motion of the oscillating flap. Comparisons between experiments and simulations validate the numerical model. Sequences of frames from a high speed camera and from numerical results are investigated to understand the physics of the slamming process. The spatial and temporal distribution of the slam pressure on the flap is presented. The free oscillating flap and the wavemaker with prescribed motion create a multiple reflection system. The re-reflection effects on the wave field, the flap dynamics and the slamming event are discussed by comparing a series of cases from experiments and simulations.