A numerical model of a dual-chamber Oscillating Water Columns (OWC) Wave Energy Converter (WEC) is built through the DualSPHysics software. This code is based on the Smoothed Particle Hydrodynamics (SPH) model, a Lagrangian meshless method where particles represent the flow, interact with structures, and exhibit large deformation with moving boundaries. A one phase approach – only water - is chosen in order to limit the computing time, as it increases with the total number of particles. The power take-off (PTO) of the system is modeled by the force applied by a vertical linear spring link on a floating plate inside the chamber. The force formula and coefficients are described, discussed, and tuned for various wave states to optimize the model. Validations against experimental data available from previous tests in wave flumes are performed. The floating plate heave of the numerical model is compared with the experimental free surface elevation. The result analyses establish the benefits and limits of DualSPHysics to model a fixed dual-chamber OWC WEC.