Epoxy resins have great modulus, high glass transition temperature, superb adhesion to large variety of fibers and chemical resistance. But the fact that epoxy resin cannot be recycled or dispersed due to permanent cross-linked structure causes them not environmentally friendly. Therefore, reinforcing biopolymers or synthetic polymers via natural fibers in place of synthetic ones within polymeric composites is good option for environmental improvement. There is increasing attention for natural fiber-reinforced composites at industrial implementations as natural fibers are appealing alternative to synthetic fibers. But, since natural fibers possess high flammability, fire behavior of the material needs to be enhanced. Fire retardant properties of polymer composites is a significant matter when environment, public health and safety are concerned. This chapter presents an overview on fundamentals for fire retardancy properties of epoxy resin based biocomposites and bionanocomposites. Tests that are utilized to evaluate flammability of epoxy resin based biocomposites and bionanocomposites and their results are reviewed.