<p>This study addresses a critical gap in the literature by developing a unified analytical model for evaluating the stability and dynamic behavior of cylindrical sandwich shells with functionally graded nanocomposite face sheets and variable-porosity cores. The model incorporates graphene nanoplatelets (GNP) and carbon nanotubes (CNT) as reinforcements, with varying distribution patterns across the nanocomposite face sheets. The governing equations are derived using Hamilton’s principle, and an analytical approach based on the state-space method is applied to compute natural frequencies and critical buckling loads under classical boundary conditions. Verification studies confirm the model’s accuracy. The results highlight the significant effects of geometric and material parameters, including reinforcement and porosity distribution profiles, boundary conditions, and shell dimensions, on the buckling and free vibration responses of the structures. Notably, increasing the porosity ratio reduces the critical buckling load and natural frequencies, while a higher nanoparticle weight fraction enhances the fundamental frequencies and critical buckling load.</p>