Shot peening is a commonly employed technique to improve the fatigue strength of nitrocarburized components. However, the compound layer of the component can be broken by this technique. Cavitation peening (CP) is an alternative shotress technique, which can increase the fatigue strength of the component without separation of the compound layer. To evaluate the potential of CP as a means for improving fatigue strength, nitrocarburaized carbon steel (JIS S50C) has been analyzed in the non-peened and CP conditions. The fatigue strength of CP specimen was achieved by the increase in the maximum hardness and compressive residual stress within the diffusion zone.