According to one embodiment, a memory system includes a nonvolatile memory, a managing unit, an order rule holding unit, a position information storing unit, a list selecting unit, a block selecting unit, a writing unit, and an updating unit. The managing unit holds for each of storage areas of the nonvolatile memory a free block list indicating free blocks. The order rule holding unit holds an order rule used to determine an order of the free block lists. The position information storing unit stores position information indicating the position of the free block list in the order rule. The list selecting unit selects the free block list corresponding to the position indicated by the position information and the block selecting unit selects the free block therefrom. The updating unit updates after the list selection the position information in the position information storing unit with position information indicating the position of the subsequently selected free block list.