Ionic polymer metal composite (IPMC) actuator is a group of electro-active polymer (EAP) which bends in response to a relatively low electrical voltage because of the motion of cations in the polymer network. IPMC has a wide range of applications in robotics, biomedical devices and artificial muscles. The modeling of the IPMC actuator is a multi-physics task as it involves the electricity, chemistry, dynamics and control fields. Due to its complexity and nonlinearity, IPMC modeling is difficult in terms of mathematics and its behavior is still not fully agreed upon by researchers. This paper presents a novel discrete-time model with state-dependent parameters (SDP) for identification of the nonlinear response of an IPMC actuator. A single-input single-output nonlinear identification algorithm is formulated and demonstrated for an IPMC actuator that exhibit both soft and hard nonlinearities. The nonlinear characteristics of the identified system are represented with coefficients which are a function of the input and output states. Following the SDP algorithm, the model is identified from input–output data to represent the model parameters as functions of past inputs and outputs. The proposed modeling approach is validated using an existing model and show exact representation of the non-linear behavior of the IPMC actuator