A memory device includes a memory cell array including a plurality of memory cells, a word line defect detection circuit electrically connected to the memory cell array through a plurality of word lines, and control logic configured to control an input/output operation of the memory cell array. When a memory defect detection command is received from a memory controller, the word line defect detection circuit is configured to provide an input voltage to a selected word line among the plurality of word lines, and to generate a fail flag based on a difference between a voltage of the selected word line and a reference voltage. When a mode register read command is received from the memory controller, the control logic is configured to transmit the fail flag and a fail row address corresponding to the fail flag to the memory controller.