Lipoma is a benign neoplasm characterized by the proliferation of well-differentiated adipocytes. The aim of the present study was to report a case of lipoma in the subcutaneous of a horse. A 5-year-old Mangalarga Marchador horse, weighing approximately 350 kg, was referred to the Veterinary Hospital with a history of increased abdominal volume. On clinical examination, a well-defined and circumscribed mass was observed in the abdomen. Surgery was performed and the material was sent for histological examination. The diagnosis of lipoma was based on macroscopic and histological characteristics of the tumor. Subcutaneous lipomas in horses are relatively rare and when located in the abdomen they must be differentiated from hernia, eventration hematoma, seroma and abscess. Surgical excision is curative, even with incomplete excision of the mass.