Green composites constitute a loosely defined family of materials which are obtained from renewable resources and are degradable through action of living organisms. These materials offer a possible alternative to traditional non-biodegradable materials where recycling is unpractical or not economical. Renewable sources of polymeric materials offer an answer to maintaining sustainable development of economically and ecologically attractive technology. When a biodegradable material (neat polymer, blended product, or composite) is obtained completely from renewable resources we may call it a green polymeric material. Nature provides an impressive array of polymers which are generally biodegradable, and which have the potential to replace many current polymers as biodegradation is part of the natural biogeochemical cycle. Natural polymers, such as proteins, starch, chitin and cellulose are examples of such polymers. In addition, Natural rubber latex (NR) Poly lactic acid (PLA) from corn and polyalkanoates (PHA) from bacteria are other green polymers.Green nanomaterials or bio nanomaterials could be easily prepared from animals and plants. These nano sized materialsâ properties are comparable to perfect crystals. In most cases, aqueous suspensions of these nano crystallites are prepared by simple mechanical stirring and acid hydrolysis process. The object of this treatment is to dissolve away regions of low lateral order so that the water-insoluble, highly crystalline residue may be converted into a stable suspension by subsequent vigorous mechanical shearing action. During the past decade, many studies have been devoted to mimic biocomposites by blending natural bionanomaterials with various polymer matrices. In this chapter, the recent advances on the preparation and characterization of different type of green nano materials and their polymer nanocomposites are discussed and reported. Macro micro and nanocomposites based on fully renewable polymers (which can be called fully green composites) and their applications are discussed in detail.