Abstract This work presents an isogeometric formulation for the geometrically nonlinear analysis of functionally graded material (FGM) plates. FGM plates are made of a mixture of two components (ceramic and metal) whose volume fractions vary smoothly along the thickness. The kinematic model is based on the Reissner-Mindlin theory for bending and shear strains and the von Karman theory for nonlinear membrane strains. Non-Uniform Rational B-splines (NURBS) are used as basis functions for the isogeometric formulation. The formulation is applied to study the buckling and post-buckling of FGM plates.