In recent years, there has been an increased use of large displacement vessels for cargo transport around the world. Due to space constraints in the matured ports, the clearance available between the approach channels and berths could not be increased or modified. Hence, the vessels passing in close vicinity to the berthed vessels has become a routine. It is essential to study the passing vessel and berthed vessel interaction for ensuring safety so that the mooring systems could be designed for the increased forces. In this paper, a study envisaging such interaction using Computational Fluid Dynamics (CFD) simulations has been attempted to determine the passing vessel effect on a moored tanker. The CFD solution used is based on a three-dimensional, unsteady, inviscid flow. Initially, the CFD simulation has been carried out for existing experimental data from published paper for validation and has been extended to a range of parameters such as passing vessel displacement, velocity, separation distance and water depth. The effect of each parameter on passing vessel forces is explained in detail. It is observed from the results that the longitudinal and transverse forces on the moored vessel become negligible for separation distance more than three times the width of the vessel. Also, the study provides a proper insight into the effect of full hull forms of various displacements on the passing vessel forces. © 2019, © 2019 IIT Madras.