In the present thesis, the buckling behavior of a simply supported piezoelectric hybrid microplate subject to thermal, electrical, and mechanical loads is studied. The size effect in the mechanical behavior of the microplate is captured by using the modified couple stress theory. The surface effects in the mechanical behavior of the microplate are captured by using surface elasticity theory and surface piezoelectricity theory. The Mindlin plate theory is adopted to describe its deflection behavior with Von-Karman’s geometric nonlinearity taken into account. Based on these assumptions and the principle of minimum potential energy, the equilibrium equations of the microplate and associated boundary conditions are derived. By applying the linear perturbation method to the equilibrium equations, closed-form solutions for the critical thermal/mechanical buckling load are obtained. Furthermore, the effects of the material length scale parameter to thickness ratio, surface tension, the applied electric field, and in-plane boundary conditions on the buckling behavior of the piezoelectric hybrid microplate are discussed in detail. The results show that reducing the size of the plates increases their resistance to buckling. In the micro dimension, surface effects do not affect the buckling behavior of the plate. It was also found that the length scale parameter in the micro dimension plays an important role so that it is not possible to study the behavior of plates in small dimensions without considering it. Keywords: Buckling, Microplate, Piezoelectric, Modified couple stress, Surface effects