In this paper the numerical modelling of an Oscillating Water Column (OWC) Wave Energy Converter (WEC) is studied using DualSPHysics, a software that applies the Smoothed Particle Hydrodynamics (SPH) method. SPH is a Lagrangian meshless method used in a growing range of applications within the field of Computational Fluid Dynamics (CFD). The power take-off (PTO) system of the OWC WEC is numerically modelled by adding a force on a plate floating on top of the free surface inside the OWC chamber. That force is implemented in the multiphysics library Project Chrono, which avoids the need of simulating the air phase that is computationally expensive in the SPH methods. Validation is carried out with experimental data received from the Korea Research Institute of Ship and Ocean Engineering (KRISO) and Ocean Energy Systems (OES) of the International Energy Agency (IEA) Task 10. The numerical and experimental water surface elevation at the centre of the OWC WEC chamber and the airflow speed through the orifice are compared for different wave conditions and different PTO systems (different orifice diameters at the top part of the chamber of the OWC WEC). Results show that DualSPHysics is a valid tool to model an OWC WEC with and without PTO system, even though no air phase is included.