In this work, the strength (sigma(1)) and thickness (t) of interphase in polymer nanocomposites reinforced with spherical nanoparticles are modeled by the developed form of Leidner-Woodhams and Pukanszky models for tensile strength. The "sigma(i)" and "t" are expressed as functions of "B" parameter in Pukanszky model and the properties of matrix and nanofiller such as the strength of matrix and the nanoparticles radius and volume fraction. Additionally, the effects of the mentioned parameters on "sigma(i)," and "t" are discussed. The calculations show that "B" has dissimilar effects on "sigma(i)" and "t" levels. A high level of "B" in Pukanszky model suggests a high level of "sigma i", while a thin interphase is obtained in this condition. Also, the content of nanoparticles plays different roles in the levels of "sigma(1)," and "t" based on the extent of interfacial adhesion between polymer and nanoparticles (B value). The influences of "B" on "t" at different nanofiller contents are described by the possibility of nanoparticles aggregation at various values of "B". (C) 2015 Published by Elsevier Inc.