This paper presents an adaptive voltage controller for secondary control (SC) of standalone AC microgrid systems, adaptive parametric estimation features inherent in Model Reference Adaptive Control (MRAC) systems. The designed controller establishes precise sharing of active and reactive power, coupled with efficient restoration of voltage reference values even in the presence of unpredictable disturbances. The proposed approach utilizes reference models to represent desired voltage behavior, while an adaptive algorithm continuously updates these models based on changing system conditions. Communication and coordination among distributed controllers enable decentralized decision-making for optimized voltage regulation. One of its key advantages lies in its simplified tuning process and a straightforward mathematical formulation, facilitating a more accessible implementation. Comprehensive simulation results underscore the superior performance of the proposed control approach compared to traditional secondary controllers, particularly in navigating voltage tracking challenges amid uncertain conditions and load fluctuations. The outcomes of this study emphasize the robustness and efficacy of the proposed MRAC as a pivotal solution for augmenting voltage stability in islanded microgrid environments.