A memory system of an embodiment includes a non-volatile memory and a memory controller. The memory controller executes a first decoding process of reading data encoded by an error correction code from the non-volatile memory and repeatedly executing bounded distance decoding on a symbol group protected by each of component codes included in N component code groups; executes a second decoding process of repeatedly executing decoding exceeding a bounded distance in units of component codes for an error symbol group determined to include an error due to a syndrome of a component code included in the N component code groups when the first decoding process fails; executes a rollback process when the first decoding process executed after the second decoding process fails; and changes a parameter used in the second decoding process and further executes the second decoding process when it is detected that the second decoding process is not progressed.