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The radiation hardness of 4H-SiC MOSFETs with LOCal Oxidation of SiC (LOCOSiC) isolation structures is evaluated in this work. NMOSFETs and PMOSFETs utilizing a 40-nm-thick thin oxide and a 200-nm-thick Field Oxide (FOX) as the gate oxide were fabricated and subsequently exposed to gamma-ray irradiation. In comparison to conventional Chemical Vapor Deposited (CVD) FOX, the LOCOSiC-isolated thin oxide MOSFETs exhibit a similar degree and trend of degradation after gamma-ray exposure. Regarding the FOX MOSFET, the positively trapped oxide charge in the FOX generated by irradiation leads to a decrease in the threshold voltage of the CVD FOX MOSFET. Conversely, the defect layer beneath the LOCOSiC FOX pins the surface potential, enabling the LOCOSiC FOX MOSFET to remain in the turn-off state even when the irradiation dose reaches 100 kGy and the gate bias increases to 24 V. These findings suggest that LOCOSiC isolation possesses exceptional radiation hardness and holds potential for application in SiC devices operating in strong radiation environments.