Acute compartment syndrome in dogs is a rare complication of muscle trauma, but it has not been previously reported as a consequence of neoplasia in dogs. This case report describes the occurrence of a compartment syndrome of the femoral compartment in an 11-year-old, male, mixed-breed dog caused by acute bleeding of an intramuscular haemangiosarcoma. The compartment syndrome was relieved by immediate fasciotomy. The dog was euthanased following acute recurrence of clinical signs seven weeks after surgery.