Mucormycosis is a rare, life-threatening, and opportunistic fungal infection that usually occurs in immunocompromised patients. Rhinocerebral and pulmonary manifestations are the common form. The rare form of gastrointestinal mucormycosis occur in all parts of the alimentary tract, with emphasis on the stomach being the most common site. Primary gastric mucormycosis following traumatic injury is an extremely rare form that is usually lethal; thus, only a few cases of survival have been reported even after early diagnosis and aggressive surgical resection, combined with antifungal treatment. We herein report a case of delayed-onset gastric mucormycosis in a polytrauma patient without predisposing factors, which was successfully treated by antifungal medical therapy alone with no surgical debridement.