Chitin nano-size fillers, i.e. nanocrystals (CHNC) and nanofibers (CHNF), were incorporated in thermoplastic starch matrix via melt-mixing. The two types of thermoplastic starch-based nano-biocomposites (S/CHNC and S/CHNF) were characterized and compared in terms of morphology, chemical and crystal structure, thermal and mechanical properties, and water resistance. In general, all thermoplastic starch-based nano-biocomposites showed better thermal stability, mechanical properties, and storage modulus than thermoplastic starch matrix without chitin nano-size fillers. This can be linked to the good dispersion of the nano-size fillers in the matrix, resulting from their chemical similarity, and also to the strong nano-size fillers matrix adhesion by hydrogen bonding interactions. The results showed that the final properties of the nano-biocomposites were dependent of the concentration and type of chitin nanosize filler introduced in the thermoplastic starch matrix. In general, the thermoplastic starch-based nano-biocomposites prepared with chitin nanofibers showed better thermal and mechanical properties and storage modulus than those prepared with chitin nanocrystals. (C) 2014 Elsevier B.V. All rights reserved.