An image encoding/decoding method and apparatus are provided. An image decoding method performed by an image decoding apparatus may comprise generating a reconstructed block for a current block, determining a target boundary for the reconstructed block, determining a first target block and a second target block based on a sample adjacent to the target boundary, and performing deblocking filtering on the sample adjacent to the target boundary, based on a prediction mode of at least one of the first target block or the second target block. In this case, a value of the sample adjacent to the target boundary may not be changed based on the prediction mode of at least one of the first target block or the second target block being a palette mode.