A memory system of an embodiment includes a memory controller and a non-volatile memory. The memory controller executes error correction encoding on user data received from a host to generate first encoded data, adds the first encoded data to each of one or more pieces of second encoded data, obtained by performing error correction encoding on each of one or more pieces of predetermined data, to generate one or more pieces of third encoded data, obtained by executing error mitigation encoding on the first encoded data, and selects any one piece of encoded data from the first encoded data and the one or more pieces of third encoded data. The non-volatile memory stores the selected encoded data.