Memory devices and methods of operating the same are provided. The memory device including at least one internal circuit including a memory cell array and a peripheral circuit configured to drive the memory cell array, a monitor logic configured to monitor a current flowing into the at least one internal circuit and output a monitoring result, a detect logic configured to detect whether a leakage current flows in the at least one internal circuit based on the monitoring result, and output detected information regarding the leakage current, and diagnosis logic configured to diagnose an error in the at least one internal circuit based on the detected information.