This research work investigates the use of environmentally friendly basalt filler as a reinforcement with polylactic acid (PLA) polymer for lightweight 3D printing applications. The 3D printing filaments were manufactured with a single screw extruder with different weight ratios of basalt filler (0, 1, 3, and 5 wt%) by maintaining the mean diameter of 1.75 mm, followed by 3D printing using fused deposition modeling technique. The results reveal that the tensile strength was insignificantly reduced with the addition of basalt filler, whereas a slight increment is observed in flexural and impact strengths for the 3 wt% filler reinforced composite. However, by preventing deformation under stress, the fillers significantly increased both tensile and flexural modulus. It conferred with the hardness test that the addition of fillers has significantly improved the Shore D hardness value in the ascending order of filler ratios. The thermogravimetric analysis results show that the neat PLA dramatically lost weight as the temperature rose because of a decreased thermal barrier, fast hydrolysis, and chain scission, whereas the basalt fillers act as a thermal barrier and prevent the early degradation of the PLA matrix in the composites. Additionally, the glass transition temperature, viscoelastic properties, and dimensional stability of the 3D-printed basalt-reinforced composites at higher temperatures were all significantly improved. According to the water absorption studies, the 5 wt% basalt-loaded composite has shown more water absorption than other composites. Overall, both 1 and 3 wt% basalt composites could be suggested for developing components like plastic gears, drone chassis, forming boards, sealing strips, and deflector strips of paper processing machines.