Background Eosinophilic polymyositis is a rare disorder in which eosinophils infiltrate muscle and supporting connective tissue structures, resembling autoimmune or immunologically mediated disease. This disorder can be associated with muscle inflammation and death, and can be a cause of atraumatic compartment syndrome. Methods This is a retrospective chart review of a case report as well as review of pertinent literature. Results This report presents a rare case of atraumatic compartment syndrome of the forearm caused by eosinophilic polymyositis. It provides a case summary and histological examination of this patient. Conclusion This is an important case to report because it highlights eosinophilic polymyositis as a unique etiology of compartment syndrome. In appropriate clinical situations where patients do not improve despite standard interventions, one should consider the rare and unusual etiology of compartment syndrome due to eosinophilic polymyositis. Furthermore, primary surgical intervention should not be delayed while waiting to ascertain a definitive diagnosis.