Polycal Wire rope isolators (PWRIs) have found many applications, especially in naval and aerospace structures. PWRIs are used to isolate individual equipment or complete floating floors against undesirable shocks and vibrations. A PWRI consists of arch shaped wire rope strands connected between circular plates. This architecture results in an isolator with a nonlinear hysteresis behavior capable of providing the necessary damping to dissipate an input energy. In this paper, a complete study of the shear cyclic behavior of PWRIs is presented. Twelve isolators of different geometries were tested in shear mode under different loading rates. The stiffness, energy dissipation, and damping were determined and related to the geometric and mechanical properties of each isolator. To overcome the limitations of existing mathematical models in representing the hysteretic behavior of wire rope isolators, a new model is proposed, in which, the Bouc-Wen-Baber-Noori model of hysteresis was adopted in conjunction with a modulating function. The model is shown to accurately replicate the soft-hardening, symmetric, hysteresis loops.