More attention has been paid to wave energy as a renewable energy source and its possibility has been studied for decades. To increase the power generation performance of a point absorber wave energy converter (WEC), the WEC with a tuned inertial mass (TIM) mechanism has been proposed and its effectiveness has been shown by the authors. The TIM mechanism was originally developed as a passive vibration control device for building structures subjected to earthquake loadings. The TIM is composed of a tuning spring, a rotational inertial mass, and a damping element such as a motor. This mechanism can increase the displacement of the damping part by taking advantage of the resonance effect of the tuning spring and the inertial mass, which results in a significant increase in power generation. To achieve further improvement, in this paper, static admittance (SA) and performance-guaranteed (PG) controllers proposed in the literature are applied to control the current into the motor for the WEC with the TIM. Numerical simulation studies under random sea waves characterized by JONSWAP spectrum are carried out to verify the advantages of a point absorber with the TIM over the conventional point absorber. Then, it is verified that the PG controlled WEC with the TIM shows even better power generation than the other approaches.