<p>In this paper, a tapered functionally graded magneto-electro-elastic energy harvester (TFGMEEEH) is considered to generate high-efficiency energy. The TFGMEEEH consists of an exponentially tapered cantilever beam with a tip mass and a re-entrant honeycomb auxetic as the core of the beam. By employing Hamilton’s principle and Ritz’s method, the governing equations of the TFGMEEEH are derived and then solved analytically. To verify the precision of the proposed model, the present findings are validated using the numerical and experimental data available in the previous studies. Also, a detailed parametric study of the influences of the gradient index, number of coil turns, tapering parameter, auxetic parameters as well as piezoelectric and magnetic resistances on the response of the system has been conducted. Moreover, the results indicate that under identical operating conditions, the generated power of the auxetic-based harvesters is 35% higher than the metal-based systems. In addition, it is found that utilizing variable cross-section in the modeling of energy harvesting systems significantly enhances the overall performance.</p>