A novel in situ rubber cure monitoring system (RCMS) has been developed for monitoring the progress of vulcanization based on the measurement of electrical properties. The sensors connected to an LCR meter were embedded in the compression mold and measured changes in the electrical properties of rubber during vulcanization. Frequencies ranging from 0.75 to 100 kHz were probed for capacitance and conductance, and 5 kHz frequency was found suitable for monitoring natural rubber vulcanization. The results show that capacitance during curing correlated with the time profile of torque from a moving die rheometer (MDR). The scorch time and optimum cure time obtained from MDR and RCMS were reported. The degree of cure and the cure rate from two methods were compared. Good correlations between the alternative methods were observed, supporting the potential of in situ RCMS during the vulcanization of natural rubber.