Additive manufacturing (3D printing) has evolved from prototyping to producing complex structures with advanced materials, enabling creative designs and reducing resource waste. However, the use of polymers in structural components is limited by their mechanical properties and long printing times. In response to the construction industry s growing demand for sustainable materials, this thesis focuses on developing biocomposites reinforced with continuous natural yarns (jute, ramie, sisal, and flax) and polylactic acid (PLA) polymer. The research covers the development of printing techniques for continuous natural yarns, thermomechanical analysis of these printed biocomposites, printed bonded joints, and large-scale production of biocomposite components. This study demonstrated the feasibility of using a large-diameter nozzle for printing biocomposites reinforced with vegetable yarns, leading to energy savings and replacing up to 48.2 percent of polymer content, thereby reducing the composite s carbon footprint. Thermal analysis confirmed that natural fibers remain intact at PLA s processing temperature, while the addition of fibers increased the composite s glass transition temperature. The primary challenge in printing continuous natural fibers was fiber impregnation, which directly impacted fiber-matrix adhesion and mechanical performance. The semi-finished filament (SF) method improved fiber bonding, resulting in superior tensile strength and elastic modulus (up to 18.4 percent higher than in-nozzle impregnation) and allowing faster printing speeds. Additionally, natural fiber reinforcement enhanced the mechanical behavior of single-lap bonded joints, particularly in bi-material applications. JFRP-wood joints exhibited the highest failure loads, demonstrating their potential for mixed sustainable structures. Furthermore, optimizing layer orientation significantly improved mechanical performance, with stiffness and strength gains of up to 35.2 percent and 80.0 percent, respectively. The findings highlight the viability of continuous natural fiber reinforcement in AM, paving the way for scalable and sustainable structural applications. Future work should focus on improving fiber-matrix interaction through pre-treatments and optimizing printing parameters to enhance composite performance.