Natural antioxidant products are receiving great attention as a safe alternative to chemically synthesized ones. For this, the phenolic compounds in the Sesbania sesban L. leaves possess potential antioxidant activities. Therefore, in this study, the Sesbania sesban L. leaf extract (SSE) was prepared and incorporated in the carboxymethyl cellulose (CMC) hydrogel as a natural antioxidant product. Firstly, the SSE was produced by the sonication-assisted extraction method, which demonstrated a total phenolic content of 61.44 ± 7.23 mg gallic acid equivalent/g dry powder weight, and a high antioxidant activity (IC₅₀ = 15.381 ± 1.270 µg/mL). Then, the SSE was loaded into the CMC hydrogel and physicochemically evaluated in terms of physical observation, viscosity, gelation time, and drug release profiles. The hydrogel showed acceptable properties with a gradual release of polyphenol content over two stages for at least 180 min. Finally, utilizing the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test, the antioxidant action of the SSE was well-maintained in the SSE loaded CMC hydrogel. In summary, the SSE loaded CMC hydrogel could be further investigated to become a potential cosmetic in the market.