<p>This paper introduces the analyses of buckling and vibration of FG sandwich piezoelectric cylindrical shells with a lightweight core exposed to a 2D magnetic field resting on viscoelastic foundations using the modified couple stress theory. In this study, Maxwell’s relations are used to derive the Lorentz magnetic force. The lightweight core is referred to as a functionally graded porous structure or a hexagonal honeycomb structure. Whereas the lower and upper layers are composed of two distinct piezoelectric materials, then a power law distribution can be used to smoothly vary the mechanical and electrical properties across the thickness. A single length-scale parameter is used in the modified couple stress theory, which accounts for the size effect. Five governing equations including Lorentz force are produced in accordance with Hamilton’s principle and the sinusoidal four-variable plate theory. To determine the critical buckling load and eigenfrequency of the FG sandwich piezoelectric cylindrical shells with lightweight core, an analytical solution to the derived equations is presented. By introducing some comparison examples, the present solution is examined. The study examines the effects of several parameters, including foundation coefficients, temperature rise, moisture concentration, material length-scale parameter, magnetic field parameter, and shell geometry, on the vibration and buckling load of FG sandwich piezoelectric cylindrical shells with a lightweight core.</p>