This chapter is about the flammability properties and flammability behaviour of bionanocomposites reinforced with the fire-retarding filler. This chapter includes the utilization of flame retardant fillers in the composites based on biopolymer and bionanomaterials as a reinforcing agent. The negative effect on the environment is observed due to the non-degradability of the synthetic composites, hence the more research work on bionanocomposite is accelerated and insisted. Bionanocomposites are versatile material but their applications are limited due to their low flame resistance properties. This chapter enlights about the authoritative solution for the improvement in fire retardancy of bionanocomposites by incorporating different fire retarding fillers and making it a potential candidate for various application where flame resistivity and thermal stability is the prime concern.