Environmental stressors such as pollution and ultraviolet radiation trigger excessive free-radical formation that accelerates skin aging, leading to dryness, fine lines, and flaking. Purple-cantigi (Vaccinium varingiaefolium (Bl.) Miq.) leaf ethanol extract delivers potent antioxidant benefits. This study formulated a peel-off gel mask to optimize bioactive delivery and evaluated its physical attributes, stability, and radical-scavenging efficacy. Following 96% ethanol maceration and extract quality assessment, three (hydroxypropyl methylcellulose) HPMC-based prototypes were prepared. Formula 3, with 3% HPMC, achieved ideal homogeneity, drying time, pH (5.8–6.2), viscosity (2,500 cP), and spreadability (5.4 cm), and remained stable under accelerated conditions. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay yielded an IC₅₀ of 34.55 µg/mL, confirming strong free-radical inhibition. The optimized peel-off gel mask offers high-performance antioxidant delivery, promising enhanced skin-protection against oxidative damage.