Memory devices and/or encoding/decoding methods are provided. A memory device may include: a memory cell array; an internal decoder configured to apply, to a first codeword read from the memory cell array, a first decoding scheme selected based on a characteristic of a first channel in which the first codeword is read to perform error control codes (ECC) decoding of the first codeword, and apply, to a second codeword read from the memory cell array, a second decoding scheme selected based on a characteristic of a second channel in which the second codeword is read to perform the ECC decoding of the second codeword; and an external decoder configured to apply an external decoding scheme to the ECC-decoded first codeword and the ECC-decoded second codeword to perform the ECC decoding of the first codeword and the second codeword.