Abstract: This study first mixed micrometer-sized and irregularly shaped Ti particles (0.5 and 1.0wt%) into the Al−Si−Mg−Zr matrix powder. Then, a novel Ti-modified Al−Si−Mg−Zr aluminum alloy was fabricated via laser-powder bed fusion (L-PBF). The results demonstrated that introducing the Ti element promoted the formation of the near fully equiaxed grains in the alloy due to the strong grain refinement of primary (Al,Si)3(Ti,Zr) nanoparticles. Besides, the presence of (Al,Si)3(Ti,Zr) nanoparticles inhibited the decomposition of Si-rich cell boundaries and the precipitation of Si nanoparticles in the α-Al cells. The ultimate tensile strength (UTS), yield strength (YS), and elongation of the as-built 0.5Ti alloy were (468 ± 11), (350 ± 1) MPa, and (10.0 ± 1.4)%, respectively, which were compared to L-PBF Al−Si−Mg−Zr matrix alloy, but much higher than that of traditional L-PBF Al−Si−Mg alloys. After undergoing direct aging treatment at 150℃, the precipitation of secondary nanoparticles led to a notable enhancement in the strength of the alloy. Specifically, the alloy achieved a maximum UTS of (479 ± 11) MPa and a YS of (376 ± 10) MPa. At 250℃, the YS of L-PBF Ti/Al−Si−Mg−Zr alloy was higher than that of L-PBF Al−Si−Mg−Zr matrix alloy due to the retention of Si-rich cell boundaries, indicating a higher thermal stability. As the aging temperature increased to 300℃, the dissolution of Si-rich cell boundaries, the desolvation of solid-solution elements, and the coarsening of nanoprecipitates led to the UTS and YS of the alloy decreasing below 300 and 200 MPa, respectively. However, the elongation increased obviously.