A 3-yr-old spayed female coyote (Canis latrans) developed clinical signs of exertional myopathy after fighting with a conspecific. A diagnosis of exertional myopathy was made based on physical examination findings, probable myoglobinuria, and elevations in serum creatinine kinase activity, alanine aminotransferase activity, and potassium concentration. Dantrolene, a hydantoin analog, as well as supportive and symptomatic therapies, was used to successfully treat exertional myopathy. This is the first reported use of dantrolene in wildlife or zoo animals.