A 5-year-old Welsh Pony mare presented with a history of dullness and inappetence and a large swelling on the left side of the neck extending to the pectoral region. Flunixin meglumine had been administered intravenously 10 days previously for treatment of laminitis. The pony was anaemic at presentation. Clostridium perfringens was isolated from an abscess overlying the left external jugular vein. Treatment consisted of supportive treatment, drainage of the abscess and administration of sodium benzyl penicillin G intravenously. A marked improvement in the mare's demeanour and a gradual increase in packed cell volume over a period of one month were observed. The historical, clinical and clinicopathological findings were consistent with immune-mediated haemolysis associated with C. perfringens infection.