This study presents a three-dimensional (3D) numerical modeling study on the backfilling process around monopiles. The numerical model utilized in the study is based on that given by Jacobsen (2011). It is composed of two main modules. The first module is the hydrodynamic model where the fluid flow conditions around the structure and near the bed are solved. The second module is the morphologic model where the sediment transport rates over the bed and around the structure are obtained and used in updating bed elevations around the structure. In the numerical model, the hydrodynamic computations are followed by morphologic computations, resulting in updated bed elevations and mesh structure which are again used to update the hydrodynamics for the next time step. In the hydrodynamic model, Reynolds-averaged Navier-Stokes (RANS) equations are solved with a k-ω turbulence closure. The morphologic model comprises five sub-modules, namely bed load, suspended load, sand slide, bed evolution and 3D mesh motion. The model is constructed in OpenFOAM CFD Package. The present model is applied to several problems of backfilling around a monopile by waves only, where the initial scour hole is generated by steady current. The numerical results appear to be in accord with the existing experimental information.