The present study investigates experimentally the effects of different shot peening treatments, including conventional, severe, over, and re-shot peening on microstructure, mechanical properties, and fatigue behavior of AIM 1050 mild carbon steel. Different shot peening treatments were performed using various effective parameters by considering the influences of increasing Almen intensity and coverage. Optical microscopy and field emission scanning electron microscopy observations and X-Ray diffraction measurements were carried out to analyze grains refinement in each shot peening treatment. Microhardness and residual stress measurements were taken from shot peened surfaces to the core material to investigate the mechanical properties. The fatigue behaviors of the specimens were examined by using the axial fatigue test. The results indicated that post-grinding, re-shot peening, and severe shot peening processes have significant effects on fatigue life improvement.