Schwannoma is a solitary, well-demarcated and generally slow-growing benign tumor arising from the from the Schwann cell in the nerve sheath. It can present in any location; however, the involvement of abdominal organ and extra-abdominal muscle are rare. In this study, we present a case with right subcostal rectus muscle schwannoma mimicking acute abdomen. The present case is the first reported case in the Turkish literature as a schwannoma of the abdominal wall. Case Report: A 47 year old female patient presented to the emergency department with complaints of severe abdominal pain and vomiting. Abdominal examination revealed right upper quadrant tenderness. In her upper abdominal ultrasound, a cystic-appearance mass lesion with a diameter of 2.5x1.5 cm was detected in right lobe anterior segment of the liver. Contrast-enhanced abdominal tomography revealed that the mass was not associated with the abdomen, but localized within the rectus muscle. Following total excision of the mass, histopathological examination demonstrated the diagnosis of schwannoma. Conclusion: Schwannomas localized inside the abdominal organs or in the abdominal wall can mimic the acute abdomen. The definitive diagnosis can be made by histopathological analyses.