An image encoding/decoding method and apparatus are provided. An image decoding method according to the present disclosure may include: obtaining palette information and palette index prediction information of a current block from a bitstream; constructing a palette predictor for the current block based on the palette information and constructing a palette table for the current block based on the palette predictor; generating a palette index map for the current block based on the palette index prediction information; and decoding the current block based on the palette table and the palette index map, wherein the palette predictor may be initialized using a user defined palette entry obtained from at least one of an adaptation parameter set (APS), a picture parameter set (PPS) or a slice header.