In this study, the nonlinear buckling and postbuckling characteristics of composite microplates made of a porous functionally graded (PFG) material are scrutinized in the presence of different size-dependent strain gradient tensors as microscale. Accordingly, for the first time, the effect of each microstructural tensor is analyzed separately on the nonlinear stability of PFG microplates with and without a central cutout. In order to fulfill this goal, the isogeometric computation approach is engaged to integrate the finite element approach into the nonuniform B-spline-based computer aided design tool. Accordingly, the geometry of the microplate with a central cutout is modeled smoothly to verify [Formula: see text] continuity based upon a refined higher-order plate formulations. In this regard, the microstructural-dependent load-deflection paths associated with the nonlinear stability of axially compressed microplates are traced.