In this paper, the effect of a static synchronous compensator (STATCOM) influence on the FREQUENCY of islanded microgrids based on FREQUENCY control using fuzzy cooperative control is investigated. To achieve fast FREQUENCY control, instantaneous power balance between generation and consumption is inevitable, and it can be supplied through energy storage systems such as battery with a proper FREQUENCY control method. Besides, the FREQUENCY control of islanded microgrids could be studied under different circumstances, where one aspect analyzed is added to a flexible AC transmission system (FACTS) device, such as STATCOM, in the microgrids. Although STATCOM is charged with improving the voltage profile, it can affect FREQUENCY stability by adjusting the voltage very quickly. Due to the importance of refining FREQUENCY stability, two controller methods are compared: a classic PI controller and a fuzzy PID controller. Accordingly, the performance of STATCOM is evaluated via two scenarios. Based on simulation results, by applying the fuzzy PID controller to the microgrid, STATCOM can reach the nominal FREQUENCY. Moreover, with greater validation and investigation of this topic, this device could be an agreeable alternative to the battery energy storage system (BESS).