With the increasing contribution of intermittent renewable generations to electric power grids, additional frequency reserves are required to manage the balance between generation and load in power systems. This paper describes the potential contribution of LED lighting loads as frequency reserves to provide ancillary services and proposes a decentralized control strategy for LED lighting loads in response to frequency deviations. Three control modes are developed according to the magnitude and duration of the frequency deviations. Experimental results verify the effectiveness of the use of an illumination controller to regulate illumination with the corresponding control modes. Simulation results demonstrate the validity of using LED lighting loads as frequency reserves to provide frequency regulation. The frequency deviations can be appropriately mitigated using the controlled LED lighting loads.