<p>The escalating global threat of ultraviolet (UV) radiation brings with itself complicated damage pathways including sunburn, inflammation and cutaneous carcinogenesis. These challenges have catalyzed sustained interdisciplinary efforts toward advanced UV-shielding technologies encompassing biomedical and environmental domains. Thus, novel sunscreen products based on sustainable biopolymers that can prevent UV-induced skin maladies are need of the hour. This study introduces an innovative multifunctional carboxymethyl cellulose/ alginate (CMCAlg) hydrogel nanocosmeceutical sunscreen formulation integrating nano zinc oxide (nZnO) and <i>Ocimum sanctum</i> (Tulsi) essential oil (TEO). TEO was extracted by ultrasound-assisted hydrodistillation method and eugenol was identified as the major constituent. The nZnO was synthesized in situ using CMC/ Alg composite as bio-template. The synthesized CMCAlg@ nZnO-TEO hydrogel, leveraging a hybrid network of Zn²⁺-crosslinking and intermolecular hydrogen bonds, demonstrated good UV-shielding capabilities and thermal stability. A slower rate of TEO release was observed in skin pH (5.5) adhering to anomalous nature of TEO release. The presence of nZnO and TEO in CMCAlg@ nZnO-TEO hydrogel synergistically improved the hygroscopic and moisturizing properties of CMCAlg@ nZnO-TEO sunscreen portraying a SPF of 20.6. Furthermore, CMCAlg@ nZnO-TEO sunscreen displayed good antioxidant and tyrosinase inhibition efficacies. Hemocompatibility assessment indicated its compatibility till 20&#xa0;mg/ mL. The CMCAlg@ nZnO-TEO sunscreen depicted no toxicity after incubation for 72&#xa0;h with 3T3 fibroblasts thereby indicating its biocompatibility. Overall, the results recommend the good potency of CMCAlg@ nZnO-TEO hydrogel for sunscreen formulations.</p> Graphical Abstract <p></p>