Hard machining, as one of the sustainable manufacturing technologies, tends to introduce highly coupled thermomechanical loads into the machined surface layer, which causes materials to suffer from severe plastic deformation underneath and, thus, the alteration of the mechanical properties. In this paper, a systemic investigation was performed on the correlation of processing parameters, plastic deformation, and mechanical properties of machined surface layer for hardened H13 steel, where the cutting parameters and tool micro-geometry are varied. The plastic deformation layer was composed of an amorphous structure and plastically deformed grain. Compared to cutting parameters, edge micro-geometry significantly influences the depth of the plastic deformation layer. The automated ball indentation (ABI) technique was utilized to evaluate the mechanical properties of the machined surface layers. Finally, the relationship between processing parameters, depth of plastic deformation, and mechanical properties was revealed. The experimental findings provide a solid foundation for processing parameter selection to improve the functional performance of manufactured components.