Multilevel inverters (MIs) have become widely used in photovoltaic (PV) systems for their high efficiency, reduced leakage currents, and reduced EMI levels. Although MIs suffer from unequal thermal stresses in power devices that lead to aging of power device with their continuous operation. Therefore, this paper proposes a new aging mitigation control (AMC) method to enhance the reliability of MIs against the aging effects in power devices. The operation of the proposed AMC method has three operating modes that are adapted according to the level and type of aging. In small and medium aging levels, the proposed method preserves the full output power ratings of the inverter with maximum energy extraction from PV modules. Whereas, in high aging level region and multiple devices failures, the proposed method reduces the output power so as to maintain continuous operation of the inverter without harmful consequences. The simulation and experimental results with comparisons to conventional methods show effective performance of the proposed AMC method.