This chapter summarizes information about the biodegradation and flame retar- dancy of PP-based biocomposites and nano composites obtained from highly ranked journals published during the last two decades. The first part of this chapter deals with the biodegradation of PP-based composites. The second part of this chapter begins with a short description of the specific flammability of PP, followed by an overview of fire retardants and flame testing methods and standards. PP composites reinforced with commonly applied cellulosic fillers, such as wood, flax and others, as well as rarely used wool fibers are considered. The effect of different nanometric fillers alone or in combination with conventional fire retardants on the flammability of composites is also described. Along with comparative analysis of different fire retardants regarding their ability to decrease the flammability of PP matrix composites, the mechanism action and their possible synergy effects are highlighted.