This research review article provides a comprehensive overview of flammability tests and fire retardant mechanisms specific to biocomposites and bionanocomposites. As the demand for sustainable materials in various industries grows, the investigation of fire safety becomes imperative. The article begins by elucidating the fundamental principles of flammability tests, addressing key methodologies employed to assess the fire resistance of biocomposites and bionanocomposites. Subsequently, the discussion delves into the intricate mechanisms underlying the fire retardancy of these bio-based materials. Emphasis is placed on exploring the inherent properties and synergistic effects of incorporating fire retardants within these composite structures. Through a systematic review of current research findings, this article aims to consolidate knowledge in the field, aiding researchers, practitioners, and industries in making informed decisions regarding the application of fire safety measures in the context of sustainable and environmentally friendly materials. The synthesis of information presented in this review contributes to advancing the understanding of flammability characteristics and fire mitigation strategies for biocomposites and bionanocomposites.