In this the paper, the problem of mitigating the seismic response of sensitive equipments housed in building structures is addressed by isolating the structure with an innovative device referred to as roll-n-cage isolator. The device is described, characterized and represented by a hysteretic semi-physical mathematical model. A numerical performance assessment is performed by implementing the isolator in a building structure housing equipment in upper floors where accelerations are amplified and motions contain strong components at long periods. The numerical results show that the proposed isolator is efficient in substantially attenuating the structure–equipment response under a wide variety of actual earthquakes while exhibiting robust performance for a wide range of structures.