Cable-sheave systems are commonly used on marine vessels for lifting and towing applications. As a result of the motion of the vessel, the cable can detach from the surface of the sheave. This thesis presents a simulation of a towed cable system which includes the interaction of the cable with the sheave surface in order to examine variations in the contact between the cable and the sheave. A three-dimensional description of the sheave geometry is implemented in order to accurately model the contact forces as the vessel undergoes six degree-of-freedom motion. To assess the performance of the model, the simulated cable behavior is compared to small scale experimental measurements. Finally, a case study was performed to demonstrate the usage of the simulation to examine variations in cable tension and contact forces for a full-scale system. The method demonstrated can be used in future studies to examine cable detachment behavior.