This study presents a novel method for 3D printing of continuous fiber-reinforced thermoplastics using fused-deposition modeling (FDM). The technique involves impregnating continuous fibers with thermoplastic resin within the heated nozzle of the 3D printer, eliminating the need for molds. The study used polylactic acid (PLA) as the matrix and carbon fibers or twisted yarns of natural jute fibers as reinforcements. The mechanical properties of the printed composites were significantly improved compared to those of conventional 3D-printed polymer-based composites and unreinforced thermoplastics. Carbon fiber-reinforced composites showed superior mechanical properties, with tensile strength and modulus 599% and 435% higher, respectively, than those of PLA. Jute fiber-reinforced composites demonstrated plant-sourced mechanical properties. The method allows for precise control over fiber direction and volume fraction, making it suitable for manufacturing load-bearing components in aerospace and automotive industries, as well as custom products in healthcare. The study also highlights the potential for further improvement by increasing the fiber volume fraction and addressing issues such as fiber-resin adhesion and voids.This study presents a novel method for 3D printing of continuous fiber-reinforced thermoplastics using fused-deposition modeling (FDM). The technique involves impregnating continuous fibers with thermoplastic resin within the heated nozzle of the 3D printer, eliminating the need for molds. The study used polylactic acid (PLA) as the matrix and carbon fibers or twisted yarns of natural jute fibers as reinforcements. The mechanical properties of the printed composites were significantly improved compared to those of conventional 3D-printed polymer-based composites and unreinforced thermoplastics. Carbon fiber-reinforced composites showed superior mechanical properties, with tensile strength and modulus 599% and 435% higher, respectively, than those of PLA. Jute fiber-reinforced composites demonstrated plant-sourced mechanical properties. The method allows for precise control over fiber direction and volume fraction, making it suitable for manufacturing load-bearing components in aerospace and automotive industries, as well as custom products in healthcare. The study also highlights the potential for further improvement by increasing the fiber volume fraction and addressing issues such as fiber-resin adhesion and voids.