Biodegradability, biocompatibility, non-toxicity, eco-friendly, and renewability make biopolymers as excellent and safe fillers for biopolymer matrices to fabricate nano-composites. However, most of biopolymers are hydrophilic and possess inadequate mechanical properties, thus uses of biopolymers in food coating and packaging are limited. There is a particular solution as follows: some particular biopolymers (cellulose, chitin, and starch) are good candidates as fillers to improve oxygen, moisture, and gas barrier and mechanical properties of hydrophilic natural polymers as continuous phases. Literature reports have shown that the above-mentioned biopolymers and their derivatives as nano-fillers improved mechanical and barrier properties of hydrophilic biopolymer matrices. The following conclusions were derived from some literature reports; (i) the advantages of bio-nanocomposites made from bio-fillers and biopolymers matrices over other bio-nanocomposites are: these nanomaterials are 100% biodegradable and recyclable, i.e., both continuous and discontinuous phases (matrix and filler) are safe for human and environment. The resulting nanocomposites are green nanomaterials; (ii) nano-bio-fillers have potential to improve gas and WVB properties of biomacromolecule continuous phases; (iii) use of nano-bio-fillers reduces cost for fabrication of desirable nanocomposites and reduce dependency to other types of fillers such as metal oxides; and (iv) use of nano-bio-fillers and biopolymer matrices in food packaging systems will certainly protect food from deterioration attacks, prolong shelf-life of food, and maintain the quality and safety of foodstuffs.