Wave power absorption with Wave Energy Converters (WECs) arrays in front of a vertical wall is predicted with an in-house transient wave-multibody numerical tool of ITU-WAVE which uses time marching scheme to solve a boundary integral equation for the analyses of hydrodynamic radiation and exciting forces. The perfect reflection of incident waves from a vertical wall is considered with method of images. Mean interaction factor, which can have constructive or destructive effect and determines the performances of WECs, is approximated with different array configurations. The vertical wall effect plays significant role over hydrodynamic parameters as the radiation and exciting forces show quite different behaviour in the case of WECs with and without vertical wall in an array system. The numerical results show that the performance and wave power absorption with WECs arrays in front of vertical wall are much greater compared to WECs arrays without vertical wall effect. This is mainly due to standing and nearly trapped waves between a vertical wall and WECs arrays in addition to strong interactions between WECs. The satisfactory agreements are obtained when the present ITU-WAVE numerical results for different hydrodynamic parameters in an array system are compared with other published analytical and numerical results.