A method and an apparatus for encoding and decoding packets using a polar code is provided. The method includes acquiring a plurality of blocks constituting the packet, extracting a plurality of codeword candidates corresponding to the blocks, selecting some of the codeword candidates in a descending order of posterior probability among the codeword candidates corresponding to the blocks, combining the selected codeword candidates into a plurality of codeword combinations, selecting a codeword combination having the highest posterior probability and passed Cyclic Redundancy Check (CRC) test without error among the plurality of codeword combinations, and decoding the selected codeword combination. The packet encoding and decoding apparatus and method of the present disclosure is capable of encoding and decoding packets in a unit of blocks efficiently.