The purpose of present study is establishing a simulation model to consider the performance of a water photovoltaic thermal system (PV/T) via the computational fluid dynamics method (CFD). The proposed model includes a water riser tube and an absorber plate to consider the conduction and convection heat transfer mechanisms. The simulation process was carried out in the ANSYS FLUENT software. The effects of two different parameters on the efficiency and performance of the system were investigated numerically. The performance of the PV/T system versus the changes in the absorbed radiation on the plate and the fluid inlet temperature were analyzed. The temperature distribution of different sections of the system was obtained. For validation of the presented method, a comparison study was carried out with the experimental results in the literature; satisfactory convergences were found between the measured data and the experimental results.