The objective of this study is to investigate the buckling response of imperfect uni-directional functionally graded material (UDFGM) sandwich plates. To conduct the buckling analysis of UDFGM sandwich plate, bi-axial compressive load is considered. In the case of the UDFGM plate, the material properties are continuously graded in only one direction, specifically the thickness direction. Typically, UDFGM plates are composed of metal and ceramic materials that exhibit different thermal and mechanical properties. In this study, we consider both even and uneven porosity distribution patterns to examine their effects on the critical buckling loads of UDFGM sandwich plates under uni-axial and bi-axial compressive loads. The effective material properties of the UDFGM plate are determined using Voigt’s micro-mechanical model with power law distributions. The sandwich plate consists of two UDFGM faces with a ceramic core. Hamilton’s Principle is employed to derive the governing equations for the buckling response of the UDFGM, using the sinusoidal shear deformation theory (SSDT). The study analyzes how uni-directional gradation, the power law index, geometric parameters, and both even and uneven porosity distribution patterns, along with the porosity coefficient, influence the buckling behaviour of UDFGM sandwich plates.