Bio-based fillers (e.g., poplar, switchgrass) have been used to reinforce polymers because of their low cost and sustainable nature. Bio-based polymers are typically produced from natural or renewable resources such as crops and herbaceous fibers. Biocomposites are commonly used in packaging, automotive, and construction applications. The filler types, filler characteristics, polymer types, and polymer characteristics are discussed and compared in this chapter. The biocomposite fabrication, performance (e.g., mechanical and thermal properties), and applications were investigated. At their end of life, biocomposites can be recycled and upcycled through various technologies, including mechanical, thermal, and chemical methods. Compared with carbon fiber–based composites, biocomposites are a cost-effective and sustainable alternative in many applications with low to moderate strength requirements.