Efficient transdermal insulin delivery to the systemic circulation would bring major benefit to diabetic patients. We investigated the possibility of using gold nanorods (GNRs) that formed a complex with an edible surfactant and insulin (INS) in an oil phase to form a solid-in-oil (SO) formulation (SO–INS–GNR) for transdermal treatment of diabetes. Diabetic mice comprised the model for our study. In vitro, there was high penetration of insulin through the stratum corneum (SC) and the dermis in mouse skin treated with an SO–INS–GNR complex plus near-infrared (NIR) light irradiation. Blood glucose levels in the diabetic mice were significantly decreased after treatment with SO–INS–GNR plus irradiation. To our knowledge, this is the first study to use gold nanorods for systemic insulin delivery through the skin. The use of an SO–INS–GNR complex combined with NIR irradiation may provide the possibility of transdermal insulin delivery to diabetic patients.