The tensile modulus of PP/nanoclay/CaCO3 hybrid ternary nanocomposite was analyzed using composite models. Rule of mixtures, inverse rule of mixtures, modified rule of mixtures (MROM), Guth, Paul, Counto, Hirsch, Halpin-Tsai, Takayanagi, and Kerner-Nielsen models were developed for three-phase system containing two nanofillers. Among the studied models, inverse rule of mixtures, Hirsch, Halpin-Tsai, and Kerner-Nielsen models calculated the tensile modulus of PP/nanoclay/CaCO3 ternary nanocomposite successfully compared with others. Furthermore, the Kerner-Nielsen model was simplified to predict the tensile modulus by volume fractions of nanofillers. Also, Takayanagi model was modified for the current ternary system. The developed Takayanagi model can predict the tensile modulus using Young's modulus and volume fractions of matrix and nanofillers. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 2309-2319, 2012