Display omitted •A mechanical vibration assisted laser direct energy deposition process is designed to manufacture SS316L/IN718 FGM.•Cracking is eliminated by mechanical vibration through refining microstructure and restraining brittle precipitations.•The deterioration of hardness and tensile properties are significantly improved by mechanical vibration.•A crack-free and reasonable-performance SS316L/IN718 FGM is successfully achieved with the mechanical vibration assistance. In this study, a mechanical vibration assisted laser direct energy deposition was used to fabricate a functionally graded material composed of stainless steel 316L and Inconel 718. The effect of mechanical vibration on the microstructure, defects and mechanical properties of the prepared functionally graded material was studied. The results indicate that in the sample without the assistance of mechanical vibration, plenty of brittle Laves phase and NbC carbides form and induce the cracking in the specific compositional gradient range from 60 % stainless steel 316L/40 % Inconel 718 to 40 % stainless steel 316L/60 % Inconel 718. The Vickers hardness obtains a minimal value near the compositional region of 50 % stainless steel 316L/50 % Inconel 718. The tensile properties are terrible with an ultimate tensile strength of 309.7 MPa and an elongation of 7.8 %. In the sample with the assistance of mechanical vibration, the synchronous mechanical vibration could effectively restrain the cracks formation in the compositional gradient region by suppressing the brittle phases precipitation, weakening the dislocation aggregation and refining the grain size, and resultantly achieve decent tensile properties with an ultimate tensile strength of 642.6 MPa and an elongation of 22.4 % and significantly improve the deterioration of hardness in the compositional gradient region.