3-O-ethyl ascorbic acid may be a good whitening ingredient in cosmetics. However, before it can be successfully used in cosmetics, its biofunctionality and stability need to be comprehensively investigated. The reduction and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging ability of this compound were analyzed to assess its antioxidant potential. In addition, the tyrosinase inhibitory ability was analyzed to show the whitening capacity of 3-O-ethyl ascorbic acid. Response surface methodology (RSM) was used to determine the optimal conditions for the ascorbic acid derivative in cosmetics. Based on the DPPH radical scavenging ability results, the half-inhibitory concentration (IC50) value of 3-O-ethyl ascorbic acid was 0.032 g/L. It also showed a good reducing ability at 1.5 g/L concentration. Based on the tyrosinase inhibition analysis, the IC50 value was 7.5 g/L. The optimal conditions to achieve the best stability were determined from the RSM as 36.3°C and pH 5.46.