This study investigates the influence of ultrasonic nanocrystal surface modification (UNSM) technique on the mechanical characteristics and fatigue life of two types of annealed and aged Inconel 718 alloys. The mechanical properties of both UNSM‐treated alloys were compared with the untreated specimens. The fatigue life of the untreated and UNSM‐treated Inconel 718 alloy specimens was investigated by ultrasonic fatigue and rotary‐bending fatigue tests. Results revealed that the UNSM‐treated specimens exhibited longer fatigue life than those of the untreated specimens. The improvement in fatigue life is mainly attributed to the induced compressive residual stress induced in the subsurface by UNSM technique.