This study explains a simple method for characterization of interphase properties in polymer nanocomposites reinforced with spherical nanoparticles. The Leidner-Woodhams model which predicts the tensile strength of interphase (sigma(i)) is properly developed, in which the stress concentration parameter is correlated with "B" interfacial parameter in modified Pukanszky model. Also, the thickness of interphase "r(i)" is expressed as a function of "B" and "sigma i" and the effects of key parameters on the properties of interphase are well discussed. The suggested equations are applied to some samples from valid literature and the values of "B", "sigma(i)" and "r(i)" are calculated. The developed model suggests logical values for "sigma(i)" which shows the applicability of the proposed model for these polymer nanocomposites. A large range for "r(i)" and "sigma(i)" is obtained for the reported samples based on the various properties of matrix, nanofiller and interphase such as "sigma(m)", "r" and "B". In addition, the results show that a larger "B" and a smaller "sigma(i)" can provide a thicker interphase in the present nanocomposites. (C) 2015 Elsevier Ltd. All rights reserved.