In this study, FSW was applied to a high nitrogen steel (HNS) containing 1.3wt% nitrogen using a PCBN tool, and feasibility of FSW for HNS, and microstructure and properties of the weld were examined. FSW produced defect-free welds in the HNS at several welding parameters. The stir zone had roughly the same nitrogen content as the base material, which suggested that both the PCBN tool wear and the nitrogen desorption hardly occurred during FSW. FSW refined the grain structure in the stir zone, which resulted in the higher hardness than the base material. Simultaneously, FSW resulted in rapid formation of Cr2N precipitates on the grain boundaries in the stir zone, which caused reduction of the corrosion resistance. This study showed that FSW is an effective method to produce a defect-free weld with high hardness in the HNS, although the corrosion resistance of the stir zone is reduced.