Silicon carbide (SiC) MOSFETs are widely acknowledged for low loss, fast switching and remarkable thermal conductivity compared to silicon (Si) counterparts; however, reliability remains a significant hindrance for the wide adoption in power electronics. Condition monitoring of SiC devices in SiC-based power converters addresses the reliability issues by providing an early sign of potential failure. One of the most consistent failure precursors of degraded SiC MOSFETs is an increase of gate leakage current. This paper presents a method of condition monitoring the SiC MOSFETs with an external circuit that indirectly estimates the gate leakage current during operation. Experimental results obtained with a prototype circuit validate the analysis and method. Reliable information can be obtained for condition monitoring at various duty ratios, dc-link voltages, and load currents in the test setup. With proper calibration, this method opens opportunities to perform prognostic and health monitoring of SiC devices using the estimated on-state gate leakage current.