A hybrid offshore renewable energy platform with multiple wind turbines and wave energy converters in a square-type host structure is proposed by Korea Research Institute of Ships and Ocean Engineering (KRISO). In this paper, we conduct a comparative study of wave run-up and slamming occurrence for the numerical simulations and physical 1:50 experiments. This hybrid renewable energy platform comprises a square frame structure with slender support structures as well as spread mooring system. Considering relative kinematics of the three-dimensional structure to waves especially for random seas, it may undergo not only vertical but also horizontal slamming impacts. Following the investigation of the wave run-up (airgap), the three-dimensional slamming occurrence is examined. Both regular waves and random waves are considered. The system identification of the numerical model is checked against the measured data from static-offset and free-decay tests. Following the systematic comparison between the experimental and numerical data, maximum wave run-up and the worst slamming occurrence in terms of the relative velocities are identified.