A deployable missile control fin has some structural nonlinearities because of the worn or loose hinges and the manufacturing tolerance. The structural nonlinearity cannot be eliminated completely, and it exerts significant effects on the static and dynamic characteristics of the control fin. Thus, it is important to establish the accurate deployable missile control fin model. In the present study, the nonlinear dynamic model of the deployable missile control fin is established. The deployable missile control fin can be subdivided into two substructures represented by linear dynamic models and a nonlinear hinge with structural nonlinearities. From dynamic tests, the nonlinear hinge parameters are identified and the nonlinear hinge model is established by the use of a system identification method such as the force-state mapping technique. The substructure modes are improved by the use of the frequency response method. The substructure models and the nonlinear hinge model are coupled to establish the nonlinear dynamic model of the fin by the use of the expanded substructure synthesis. Finally, the established nonlinear dynamic model of the deployable missile control fin is verified by modal and dynamic tests. The established model is in good agreement with test results, showing that the present approach is useful in aeroelastic stability analyses such as time-domain nonlinear flutter analysis.