Purpose <p>Functionally graded materials offer unique opportunities for designing structural components with tailored properties. This study uses a higher-order shear deformation theory to investigate the free vibration behavior of epoxy-based functionally graded beams. </p> Methods <p>The theoretical formulation considers the shear deformation effects more accurately than classical beam theories, thereby providing more accurate predictions of the beam dynamic response. Assumptions for material properties gradation are based on power law distribution through the axial direction. The governing equations of motion are derived by incorporating the higher-order shear Deformation theory and solving the corresponding eigenvalue problem. The numerically obtained values are natural frequencies and mode shapes of the AFG beam solved by adopting the Navier-type solution method.</p> Results <p>The natural frequencies are influenced by an increasing trend with a decrease in the volume fraction gradient of GPL, and also with an increase in length-to-thickness ratio. The natural frequencies increased by 53.12 % in the S-S condition, and 50.86 % in the C-C condition for the third mode of vibration by increasing the slenderness. The proposed shear deformation theory provides more accurate predictions of the natural frequencies as compared to classical beam theories with a minimal error of 48.65 % in the C-F condition.</p> Conclusions <p>The key findings of this study contribute to the understanding of the dynamic behavior of functionally graded beams and provide valuable insights for the design and analysis of FGM-based structures subjected to free vibrations.</p>