A memory controller is provided. The memory controller includes an error correction code (ECC) circuit configured to correct an error of a read codeword provided from a memory device, the ECC circuit including: a codeword combination generator configured to receive a first read codeword including a plurality of first read codeword bit values that are read from a first region of the memory device, generate a change codeword by changing values of one or more of the plurality of first read codeword bit values, and provide a codeword combination including the change codeword; and an ECC decoder including a plurality of ECC engines, wherein the ECC decoder is configured to perform ECC decoding in parallel on a plurality of codewords included in the codeword combination.