Necrotizing fasciitis, although rare, is one of the more serious, life-threatening complications of missed acute appendicitis. Patients who are predisposed to developing necrotizing fasciitis, regardless of the cause, are typically immunocompromised. We present a case of a 49-year-old immunocompetent female whose diagnosis of acute appendicitis was missed and who subsequently developed necrotizing fasciitis of the abdominal wall and flank. She recovered 1 month after admission due to aggressive surgical and medical therapy.