A three-dimensional analytical micromechanical model based on unit cell is extended and presented to extract the electro-thermo-mechanical properties of short Carbon Nano-Tube (CNT) reinforced piezo-polymeric composite. Representative volume element (RVE) of the piezonanocomposite consists of three phases including CNT, piezo-polymeric matrix and interphase region. The presented model considers the CNT as a transversely isotropic solid fiber and CNT/matrix interphase region possessing van der Waals’ interaction as an isotropic hollow cylindrical solid that its mechanical properties are derived using the equivalent continuum model. Both phases are considered linear elastic. Also, the matrix is a piezoelectric material that is mechanically isotropic and elastic, and polarized along the perpendicular direction to CNT axis. The state of CNT arrangement within the matrix is assumed to be regular and square. First, the results obtained from the model are compared with available researches. Then, the effects of CNT volume fraction and aspect ratio and interphase effective thickness on the overall properties of the nanocomposite are investigated. In this study, despite the prior works, all the piezo-electro-thermo-mechanical properties of the nanocomposite are studied. The results show that even small amount of FVF has significant effect on improving the composite properties. Furthermore modeling of interphase region includes a great effect on the most of the composite properties, thus its modeling is necessary for more actual prediction about the nanocompite response.