<p>Additive manufacturing (AM), more commonly known as 3D printing, has transformed the process of fabricating composite materials by providing the benefits of creating complex shapes and tailored material distribution. Conventional fibers present environmental challenges, leading to a shift toward eco-friendly alternatives such as basalt fiber. This study investigates the mechanical properties of biodegradable polymer, polylactic acid (PLA), reinforced with continuous basalt fiber (CBF) fabricated using material extrusion 3D printing. Specimens with different fiber volume fractions and raster orientation patterns were 3D-printed and experimentally tested. The identified modes of failure were explored using scanning electron microscopy (SEM). Results showed significant improvements in mechanical performance with increased basalt fiber content. The tensile toughness increased by up to 381%, and the ultimate strain improved by 12%, depending on the fiber volume fraction and raster orientation. Similarly, the flexural toughness improved by up to 235%, while the flexural strain reduced by a maximum of 41% with higher fiber content. Additionally, the tensile and flexural strengths of composite specimens with 20% fiber content increased by up to 430 and 111%, respectively, compared with neat PLA specimens. The rule of mixture (ROM) was employed to predict the mechanical properties of CBF-reinforced composites. The experimental results closely approached the upper limits of the predicted mechanical properties. Challenges such as the expansion of CBF after extruding from the nozzle and layer shifting were also identified. These findings highlight the potential of CBF-reinforced PLA composites for applications demanding high specific strength and environmentally friendly materials.</p>