The mechanical properties of shape memory alloy/epoxy composites are evaluated using cylindrical representative volume element for long and short shape memory alloy wires considering the effect of interface between shape memory alloy wires and epoxy resin. The cohesive zone model is used to simulate the interface region between the shape memory alloy wire and the resin. An experimental pullout test is performed on the cylindrical specimens of resin containing single-shape memory alloy wire in order to achieve cohesive zone parameters. The finite element method is utilized to characterize the elastic properties of shape memory alloy/epoxy composites including axial modulus, transverse modulus, and Poisson’s ratio. The effect of length ratio between the shape memory alloy wire and the representative volume element on the mechanical properties of composite is investigated. Moreover, the critical aspect ratio for short shape memory alloy wires is calculated using shear-lag model.