We have successfully performed femtosecond laser peening on a 2024 aluminum alloy, which was not covered with any sacrificial overlays such as a protective coating, nor using water as a plasma confinement medium during the peening treatment, in air. The femtosecond laser peening process has a great potential to be applied in various fields where conventional peening methods cannot be used, as this process can be performed under ambient conditions without the use of a sacrificial overlay on the material.