Cysticercosis is a disease caused by encysted larvae of the tapeworm Taenia solium. Most muscular disease presents with central nervous system involvement or multiple cysts or both. The authors report a 25-year-old woman with a rare single muscle cyst presenting as a tender hard triceps mass. Results of clinical examination and magnetic resonance imaging were indicative of a soft tissue tumor. Excision of the mass revealed purulence, and the histologic diagnosis was cysticercosis. In the differential diagnosis of isolated muscular masses, a rare isolated cysticercus presenting as a pseudotumor should be considered.