Leg ulcers affect millions of people worldwide, and are a significant cause of morbidity and mortality. Various factors can be etiological agents of leg ulcers such as vascular, neuropathic, infectious, and traumatic factors. Treatment of the leg ulcer can be difficult in some cases despite using different systemic treatments and local wound care, but various newly defined treatment modalities are discussed in the literature and topical insulin application is one of them. Insulin is a hormone that is essential for regulating blood glucose and lipid levels, also insulin can have local effects when applied topically. Various mechanisms like regulation of inflammation, collagen synthesis, and angiogenesis have been explained to understand topical insulin's effects on the wound. There are case reports and studies on the usage of topical insulin on diabetic ulcers and decubitus ulcers. We applied topical insulin as an add-on therapy on a treatment-resistant leg ulcer and observed the healing of the lesion. The use of topical insulin as an add-on therapy may reduce treatment time and speed up wound healing. Topical insulin can be considered as an additional therapy for treatment-resistant ulcers.