In order to enhance the mechanical properties of the selective laser-melted (SLM) high-Mg content AlSiMg1.4 alloy, the Zr element was introduced. The influence of Zr alloying on the processability, microstructure, and mechanical properties of the alloy was systematically investigated through performing microstructure analysis and tensile testing. It was demonstrated that the SLM-fabricated AlSiMg1.4-Zr alloy exhibited high process stability with a relative density of over 99.5% at various process parameters. Besides, the strong grain refinement induced by the primary Al₃Zr particle during the melt solidification process simultaneously enhanced both the strength and plasticity of the alloy. The values for the yield strength, ultimate tensile strength, and elongation of the SLM-fabricated AlSiMg1.4-Zr were (343±3) MPa, (485±4) MPa, and (10.2±0.2)%, respectively, demonstrating good strength- plasticity synergy in comparison to the AlSiMg1.4 and other Al-Si-based alloys fabricated by SLM.