The nonlinear aeroelastic characteristics of a deployable missile control fin have been investigated. Modes from free vibration analysis and a doublet-point method are used for the computation of supersonic unsteady aerodynamic forces. The minimum-state approximation is used to approximate the aerodynamic forces. The fictitious mass modal approach is applied to reduce the problem size and the computation time in the linear and nonlinear flutter analyses. For the nonlinear flutter analysis, the deployable hinge is represented by an asymmetric bilinear spring and is linearized using the dual-input describing function method. From the nonlinear flutter analysis, three different types of limit-cycle oscillations are observed in the wide range of airspeed over the linear flutter boundary. The aeroelastic characteristics of the missile control fin can become more stable due to the existence of the deployable hinge nonlinearity.