Reactive oxygen species (ROS), commonly recognized as free radicals, significantly contribute to skin damage by disrupting defense and repair mechanisms, thereby accelerating the aging process. An effective strategy to prevent and alleviate skin aging involves the application of topical formulations enriched with powerful antioxidant compounds. Sacha inchi oil (Plukenetia volubilis L.) has been reported to possess significant antioxidant activity, while its oil contains a high content of omega-3 fatty acids, offering potential anti-aging benefits. This study aims to evaluate the stability, in vitro anti-aging activity, and skin irritation assessments of a facial serum containing Sacha inchi oil (SIO) formulated as a topical anti-aging agent. The stability of the serum was assessed by analyzing its organoleptic properties, homogeneity, viscosity, spreadability, pH, microbial contamination, and heavy metal content over a three-month period under controlled climatic conditions. The in vitro anti-aging activity was evaluated through enzyme inhibition assays for neutrophil elastase and collagenase, while skin irritation was assessed via human patch testing. The results indicated that the SIO facial serum exhibits excellent stability, significant anti-aging activity, and is safe for topical application, with no irritant effects observed during skin irritation assessments.