This chapter explores the synthesis, properties, and applications of polylactic acid (PLA)/polyhydroxybutyrate (PHB) biodegradable polymer blends, particularly in the context of fused deposition modeling (FDM) 3D printing. PLA and PHB, derived from renewable resources, offer promising alternatives to traditional petroleum-based polymers, contributing to environmental sustainability. This chapter summarizes the advantages of PLA and PHB, such as their biodegradability, biocompatibility, and mechanical properties, and how these characteristics can be optimized through 3D printing techniques. The chapter further discusses the impact of various FDM process parameters on the mechanical properties of PLA/PHB blends, including deposition angle, filling density, layer thickness, wall thickness, and printing temperature. The optimal printing conditions are suggested to enhance the mechanical strength and overall performance of the printed products. Moreover, the chapter reviews the diverse applications of PLA/PHB blends in fields such as environmental protection, biomedical engineering, aerospace, packaging, architecture, and artistic creation. The combination of PLA and PHB in FDM technology is shown to have significant potential, although challenges such as stability, durability, and cost-effectiveness remain. The chapter concludes with a discussion on the future outlook, emphasizing the need for further research to optimize PLA/PHB blends for broader industrial applications and to overcome existing limitations.