A memory device includes a memory cell array including memory cells arranged in a plurality of rows; an ECC engine configured to detect an error in first data that is read from the memory cell array in response to a read command and a read address, to output a first error occurrence signal, and to correct the error in the first data; a row fail detector configured to output a fail row address, which indicates a fail row among the plurality of rows; and a flag generator configured to receive the read address, the first error occurrence signal, and the fail row address, and to generate a decoding state flag, which indicates whether an error is detected and whether an error is corrected, and a fail row flag, which indicates that a read row address included in the read address is the fail row address.