Pyomyositis is defined as suppurative infection of the skeletal muscle and usually occurs in immunocompromized patients. We managed a 23-year-old man admitted for myalgia and evidence of infection, with onset after a strenuous physical activity. Numerous muscles were involved. Multiple abscesses were visualized by ultrasonography and computed tomography, with predominant involvement of the pelvic muscles. Examination of the aspirate from a forearm abscess recovered Staphylococcus aureus. No factors associated with immunodeficiency were found. Appropriate antimicrobial therapy ensured complete resolution of the infection. Pyomyositis is rare in immunocompetent individuals. Myalgia, fever, and rhabdomyolysis should suggest pyomyositis. Computed tomography and magnetic resonance imaging are the best investigations for confirming the diagnosis.