This paper assesses the vibratory energy harvesting performance of a tuned inertial mass electromagnetic transducer (TIMET) through hardware-in-the-loop (HIL) testing under random vibration. The TIMET has been developed by adding a tuning spring and an extra rotational inertial mass to a conventional electromagnetic transducer (ET) with a motor. The authors have already shown that the energy harvesting efficiency of the TIMET can be increased by taking advantage of the mechanical resonance effect of the rotational inertial mass due to the tuning spring through numerical simulation studies. In addition, further improvement in power generation of the TIMET can be achieved theoretically by controlling the current to the motor based on the appropriately developed algorithms. In this paper, the superiority of the TIMET over the ET under random disturbances when the current to the motor is controlled by the algorithms proposed for the ET in the literature is experimentally verified. Moreover, the accuracy of the numerical simulation using the developed device models is validated by comparing with the test results.