In this paper, sandwich plates with one porous polymeric core and two carbon nanotube (CNT)/polymer nanocomposite outer layers were proposed as ultra-lightweight engineering structures. The distribution of pores and CNTs were assumed to be functionally graded (FG) along the thickness of core and nanocomposite layers, respectively. Moreover, the important effect of the formation of CNT clusters in nanocomposite layers were considered. Specifically, thermoelastic static responses of proposed porous nanocomposite sandwich plates (PNSPs) subjected to thermal gradient and mechanical loads were presented in terms of deflection and stress distributions. Governing thermoelastic equations derived from total energy function were facilitated using a mesh-free method in combination with two plate theories. Furthermore, Eshelby-Mori-Tanaka’s approach was utilized to estimate the temperature-dependent material properties of the resulted CNT clusters/polymer nanocomposite. The effects of CNTs and porosity characteristics, thermal and mechanical loadings, geometrical dimensions, elastic foundation coefficients and boundary conditions on the bending and stress distributions of the proposed PNSPs were investigated. The results showed that sandwich plates with FG porous cores had less deflection compared with those containing UD cores. Moreover, due to the formation of CNT clusters, adding more than 5% volume fraction of CNTs had an insignificant effect on the deflection of PNSPs.