The progression of climate change has intensified marine environmental conditions, increasing wave energy and exacerbating the vulnerability of coastal infrastructure. Among coastal defense structures, vertical breakwaters are widely adopted for their spatial efficiency but suffer from excessive wave reflection, which adversely affects harbor tranquility and vessel safety. This study investigates a vertical breakwater integrated with an Oscillating Water Column (OWC) device as a dual-purpose structure for wave protection and renewable energy generation. Previous studies have demonstrated the feasibility of OWC systems through full-scale installations and numerical modeling. In this study, two-dimensional wave flume experiments were conducted to evaluate the reflection coefficient and energy conversion efficiency under various wave conditions. Notably, the efficiency (η) reported here represents chamber capture efficiency excluding turbine/orifice losses. In practical systems, an additional pneumatic-to-electric efficiency of approximately 60–80% is typically expected. The results reveal the interdependence between wave reflection and energy absorption, providing fundamental insights into the optimization of breakwater-integrated OWC systems.