In this study, spin welding was used to join 3D-printed (3dp) and solid acrylonitrile–butadiene–styrene (ABS) rods. The fused filament fabrication method was utilized to make the 3dp ABS rods. These rods had a diameter of 12.5 mm and internal fill percentages of 50, 75, and 100. At three different spindle speeds, 710, 1000, and 1400 rpm, two distinct joints were created: 3dp/3dp and 3dp/solid joints. These weld joints' tensile characteristics were investigated. The fracture section of the joints was analyzed employing field-emission scanning electron microscopy, and the causes for the fracture of the joints were explored. Furthermore, the effects of the fill percentage and spindle speed on the joint's tensile strength were studied using analysis of variance (ANOVA). Moreover, functional predictive equations for estimating weld strength were established. According to the results, the joints typically failed due to brittle fracture in the 3dp component of the weld joints. Furthermore, it was found that increasing the fill percentage and spindle speed enhanced the tensile strength of the weld joints. Moreover, 3dp/solid joints were stronger than 3dp/3dp joints. Highlights: Spin welding of 3D-printed and solid ABS rods was done for the first time. The effect of spindle speed and fill percentage on the tensile characteristics of 3D-printed/3D-printed and 3D-printed/solid joints were investigated. Comprehensive FESEM analysis was carried out, and the reasons for the joint fracture were examined. [ABSTRACT FROM AUTHOR]