<p>Cold spray, conventionally a powder consolidation process to deposit materials, shares many attributes with the shot peening process that is used to strengthen metal surfaces. It is possible to take advantage of the high particle impingement velocity achieved by the cold spray equipment and use the process as a high-velocity shot peening process to strengthen metal surfaces. Cold spray shot peening (CSSP) is an emerging surface engineering technique that integrates the high-velocity particle impact of cold spray with shot peening to enhance the mechanical properties of metallic materials. In this work, interstitial-free (IF) steel was used to explore the potential of CSSP in enhancing material surface and its mechanical properties. Results show that after different numbers of passes of CSSP, gradient microstructure was obtained, and grain refinement was achieved in the surface region. Repeated bombarding of the IF steel surface can increase its surface hardness by 53% after 125 passes of CSSP. Tensile testing results suggest that CSSP can significantly enhance yield strength. In particular, the sample after 125 passes of CSSP exhibits a yield strength approximately twice that of the as-received material while maintaining a comparable uniform elongation, thereby achieving a good combination of strength and ductility. The results of this work demonstrated that CSSP can effectively improve both surface hardness and the bulk tensile behavior of IF steel.</p>