Composite materials have received significant attention from researchers and engineers over the past decades. With several fascinating merits offered by composite materials, the steady growth of such materials in various engineering sectors has been witnessed. However, one of the critical weaknesses of most composite materials is associated with their poor fire retardancy properties, which lead to material decomposition and the release of toxic substances upon burning. When dealing with biocomposites incorporated with cellulosic fibers, it is particularly vital to understand their fire retardancy potential as these materials are generally highly flammable. Since biocomposite materials have been employed in various engineering applications, it is essential to improve their fire retardancy to lessen the risk of catastrophic failure. This chapter intends to provide a comprehensive understanding of the combustion mechanism and the techniques for enhancing the flame retardancy of composite materials. In addition, this chapter also aims to delve deeper into the flammability of cellulosic fibers, flame retardancy of biocomposites and eco-friendly flame retardants that have immense potential to develop flame-retardant biocomposites. This chapter is expected to enhance the understanding of the readers by providing a comprehensive overview of the fire retardancy of biocomposites.