In this study, composite specimens were produced using the stereolithography (SLA)-based 3D printing method by reinforcing an acrylonitrile butadiene styrene (ABS)-based polymer matrix with 1 wt% of 3 mm long glass fibers. The aim of the study is to investigate the effect of low-ratio fiber reinforcement on the mechanical performance of parts produced via the 3D printing process. The glass fiber additive was homogeneously dispersed within the resin via mechanical mixing, followed by the fabrication of specimens using the SLA method. Tensile and flexural tests were conducted on the produced neat ABS and 1% glass fiber-reinforced composite specimens. The obtained results indicated that the low fiber content did not yield a significant increase in the tensile and flexural strength of the material. Weak fiber-matrix interfacial bonding and low fiber volume are considered the primary reasons for this outcome. In conclusion, the mechanical improvement effect of low-ratio glass fiber reinforcement remained limited in ABS-based composites produced via the SLA method. For future studies, it is recommended to increase the fiber content, perform surface modifications, or optimize parameters controlling fiber orientation.