Waste rubber disposal causes considerable negative environmental impacts due to its increase worldwide, mainly in the automotive industry. Therefore, the search for technological solutions for rubber waste is a priority, and the first step in this material degradation is devulcanization due to its difficult degradation. This study evaluated rubber devulcanization using a closed vessel microwave digestion system with nitric acid (HNO3) and hydrogen peroxide (H2O2) through chemical characterization, aiming at verifying the synergistic effect between these oxidizing agents. Microwave irradiation was applied as a heating method to facilitate the chemical reactions, focusing on the synergism between HNO3 and H2O2. Results showed that 5 M H2O2 in combination with 1% HNO3, presented better results. A greater decrease in cross-link density was demonstrated as the concentration of H2O2 increased (3.96·10–5±1.99·10–6 mol/cm3), likewise, higher sulfates released (926.8±53.4 mg/L), increased mass loss (12.184±1.06%), rubber surface fragmentation, and important variations in the C–S, C=O bands, showing better results when devulcanization is carried out in synergism between HNO3 and H2O2.