Functionally graded materials are composite materials used to build a variety of structures. The porosity made in these materials may negatively affect some behavior aspects like stiffness and strength, but it may provide superior performance in other fields like vibration reduction, thermal isolation, energy absorption, and others. In this paper, we will discuss the effect of porosity on the natural frequencies for functionally graded porous (FGP) sandwich beams. The mechanical properties of the FGP sandwich beams change with the thickness direction's porosity. The free vibration of the beams is examined with the effect of porosity. The analysis is carried out for four different beam supporting types (hinged – hinged, fixed – fixed, free, fixed – hinged). Various porosity ratios are considered with a range from (0.1 – 0.9). Forty–four samples are analyzed for each type of core material distribution which is the symmetric material constitutive relationships (SMCR) and uniform core material. The results gained from the analysis show that the porosity constant has a significant effect on the natural frequencies of the FGP sandwich beams.