In this study, first of all, the mathematical model of an unmanned surface vehicle (USV) is provided. Particle swarm optimization (PSO) based proportional-integral-derivative (PID) and fractional order PID (FOPID) controlllers are designed to control yaw position (heading) of the modelled USV. The gain parameters of the PID controller and the gain and order parameters of the FOPID controller are determined by using PSO algorithm. The performance of the designed controllers are compared in terms of tracking the various step inputs and rejecting the disturbances. Simulation studies performed using Matlab software demonstrate that the FOPID controller provides better performance in the control of USV.