In this study, mathematical modeling was used to investigate the influence of nanofiller nanocrystalline cellulose (NCC) on the mechanical and barrier properties of the polymer matrix consisting of poly(lactic acid) (PLA), poly (butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS). The modified Halpin-Tsai equation was used to model the elastic modulus of the nanocomposites, while the modified Nielsen equation was used to model the water vapor permeability (WVP) as a function of nanofiller content, geometry, strength and interactions with polymer matrix. The theoretical predictions for modulus from the modified Halpin-Tsai model were close to the experimental results. This model predicted that the increase in aspect ratio and modulus of nanofiller leads to the increase in modulus of the nanocomposites. The experimental results of WVP were close to the theoretical predictions of modified Nielsen's model. This model predicted that the increase in aspect ratio and surface interaction of fillers with the polymer matrix leads to decrease in WVP. The theoretical predictions and experimental values show an increase in modulus and decrease in WVP with increase in nanofiller content. Therefore, these models could be used to understand the influence of more effective fillers on the mechanical and barrier properties of the nanocomposites.