Magneto-rheological elastomers (MREs) have attracted notable credits in the development of smart isolators and absorbers due to their controllable stiffness and damping properties. For the purpose of mitigating unwanted structural and/or machinery vibrations, the traditional MRE based isolators have generally proven effective because the MR effect can increase the stiffness when the magnetic field is strengthened. This study presents a novel MRE isolator that its stiffness was reduced when the applied current was increased. This innovative work was accomplished by applying a hybrid magnet (electromagnet and permanent magnets) onto a multilayered MRE structure. To characterise this negative stiffness concept, a multilayered MRE isolator with a hybrid magnet was first designed, fabricated, and then tested to measure its properties. An obvious reduction of the effective stiffness and natural frequency of the proposed MRE isolator occurred when the current was continuously adjusted. On the other hand, this device could also work as a conventional MRE isolator as its effective stiffness and natural frequency also increased when a negative current was applied. Further testing was carried out on a 1-degree-of-freedom system to assess how effectively this device isolated vibration. In this experiment, two cases were considered, and in each case vibration of the primary system was obviously attenuated under ONOFF control logic, thus demonstrating the feasibility of this novel design as an alternative adaptive vibration isolator. For the convenience of developing advanced control algorithms, a phenomenological model was adopted to predict the behavior of the MRE isolator. The fitting results prove the feasibility of this model of capturing the behaviors of the isolator. Additionally, further simulation work was done to evaluate the effectiveness of the reference following sliding controller on vibration isolation by using the phenomenological model presenting the real MRE isolator. The simulation results show that the semi-active system achieves much better displacement and acceleration responses than the passive systems.