This paper is concerned with the question of control of the rotation angle of a projectile’s fin using a piezoelectric beam actuator. The smart fin system considered in this paper consists of a hollow rigid fin (or canard) and a flexible beam actuator. A finite element model of the fin-beam model is developed. The model also includes aerodynamic forces acting on the fin. The rotation angle of the fin is controlled by deforming the beam actuator, which is hinged at the tip of the rigid fin. First, a state feedback adaptive control law is designed for the trajectory control of the fin angle. This is followed by the design of an adaptive control system using only output feedback (fin angle and its derivative). In the closed-loop system, asymptotic trajectory tracking of the fin angle is accomplished. Simulation results are presented, which show that trajectory control of the fin angle is accomplished using state as well as output feedback, in spite of large uncertainties and aerodynamic disturbance forces, and the flexible modes remain bounded during maneuvers.