This paper advanced our recent effort (Li and Çalışal, 2007, “Preliminary Result of a Discrete Vortex Method for Individual Marine Current Turbine,” The 26th ASME International Conference on Offshore Mechanics and Arctic Engineering, Jun. 10–15, San Diego, CA) to study the behavior of tidal-current turbines. We propose a discrete-vortex method with free-wake structure (DVM-UBC) to describe the behavior of a stand-alone tidal-current turbine and its surrounding unsteady flow and develop a numerical model to predict the performance and wake structure of the turbine based on DVM-UBC. To validate this method, we conducted a series of towing tank tests. DVM-UBC is then validated with several kinematic and dynamic results. When we compared the results obtained with DVM-UBC with our towing tank test results, published results, and the results obtained with other numerical methods, we achieved good agreements. Our comparisons also suggested that DVM-UBC can predict the performance of a turbine 50% more accurately than the traditional discrete-vortex method (traditional DVM) with comparable computational effort and will produce results comparable to the Reynolds averaged Navier–Stokes equation with much less computational effort.