<p>This research article examines the free vibrational behavior of composite laminated sandwich plates with a partially treated graphene-reinforced magnetorheological elastomer (GMRE) core. Experimental analysis was conducted to determine the natural frequencies of the partially treated sandwich plates under varying magnetic field intensities and clamped–clamped (CC) boundary conditions. A finite element (FE) model was developed using Abaqus to simulate the dynamic response of the sandwich plates. FE model results have been validated against the experimental findings and the published literature. Parametric studies were performed to examine the effects of magnetic field, boundary conditions, aspect ratio, patch size, and fiber ply orientation on different plate configurations. The results indicate that the size and location of the GMRE-treated regions significantly affect the natural frequencies, irrespective of the magnetic field. These findings demonstrate the potential of the partial treatment as a compact and adaptable approach for controlling vibrations in advanced composite structures.</p>