Abstract In this paper free vibration and bending analyses of a sandwich microbeam with two integrated piezo-magnetic layers as sensor and actuator are studied. Strain gradient theory of micro-structures is used to derive the governing equations of motion. First-order shear deformation theory as well as strain gradient theory is used for this purpose. The micro-piezo-magnetic layers are subjected to applied electric and magnetic potentials. The sandwich microbeam rests on visco-Winkler-Pasternak foundation. Electric and magnetic potentials are assumed as combination of linear function along the thickness direction that reflects applied electric and magnetic potentials and a cosine function that satisfies boundary conditions. Numerical results of this problem investigates the effect of some important parameters of sandwich microplate such as three micro length scale parameters, applied electric and magnetic potentials and parameters of foundation on the magneto-electro-mechanical responses of the problem.