In this study, we propose an adaptive droop control strategy for application to hybrid static synchronous compensator (STATCOM) systems. The proposed voltage sensitivity-based adaptive droop control scheme using a hybrid STATCOM system helps eliminate any possible interference from other voltage regulation devices while achieving better voltage regulation without implementation of a full observation of the corresponding network. Sensitivity analysis was performed by voltage control of the STATCOM system, and sliding-mode control was included for robustness of the control system. The fixed and adaptive control methods were compared through case studies of the IEEE 39-bus test system. A transient simulation of the hybrid STATCOM system by considering both low- and high-penetration levels of inverter-based resource.