In this article, electro-thermo-mechanical vibrational behavior of functionally graded piezoelectric (FGP) plates with porosities is explored via a refined four-variable plate theory for the first time. Uniform, linear and nonlinear temperature changes are considered in this study. Electro-elastic material properties of porous FGP plate vary across the thickness based on modified power-law model. The governing equations derived from Hamilton's principle are solved analytically. The exactness of solution is confirmed by comparing obtained results with those provided in the literature. Influences of applied voltage, porosity distribution, thermal loadings, material gradation, plate geometrical parameters and boundary conditions on the vibrational behavior of FGP plates are discussed. These results can be applied for accurate design of smart structures made of functionally graded piezoelectric materials by considering porosity distribution.