© 2018 Elsevier B.V. We succeeded in improving the fatigue properties of friction stir welded 7075-T73 aluminum alloy, e.g., prolonging the fatigue life at lower stress amplitude as compared to the base metal, using femtosecond laser peening, which was performed in air without any overlays such as a protective coating and plasma confinement medium, which are necessary for conventional nanosecond laser peening. The results of the plane bending fatigue tests with a stress ratio of R= -1 demonstrated that femtosecond laser peening enhanced the fatigue strength of the friction stir welded specimen at 106cycles by approximately 15 MPa compared with that of the base metal, and prolonged the fatigue life of the friction stir welded specimen under cyclic loading at a stress amplitude of 200 MPa by approximately 3.7 times compared with that of the base metal. We suggest that dislocation generation, which occurs behind the shock front under femtosecond-laser-driven shock compression owing to its large shock amplitude, induces surface hardening and compressive residual stresses in a near-surface volume. They prevent the initiation of fatigue cracks on the surface of the specimen, resulting in improved fatigue properties.