In this paper, for the first time, displacement and stress analysis of bidirectional functionally graded (BDFG) porous sandwich beams are developed using the Chebyshev tau method. Based on the presented approach, sandwich beams under non-uniform load rested on Winkler/Pasternak foundation are analyzed. The material properties of core and each face sheet can be varied continuously in the axial and thickness directions, also the material properties are affected by the variation of temperature and moisture. To overcome some of the shortcomings of the traditional equivalent single layer theories for analysis of sandwich structures, governing equations are extracted based on the layerwise theory and five coupled differential equations are obtained. The resulting differential equations are solved using the Chebyshev tau method (CTM). The effectiveness of the CTM is demonstrated by comparing the obtained results with those extracted from the ABAQUS software. The comparisons indicate that the applied method to solve the systems of ordinary differential equations is efficient and very good accurate.