Gastrointestinal stromal tumors are mesenchymal neoplasias which are derived from Cajal's interstitial cells. The most common site of involvement is the stomach. It may be multiple in patients with Neurofibromatosis Type-1, while the small intestine is the most common location. In this case report, we aimed to present a Neurofibromatosis Type-1 patient, showing coexistence of multiple gastrointestinal stromal tumors in the stomach and small intestine with a signet ring cell carcinoma in the stomach. A 74-year-old female patient with poor appetite, vomiting and stomach ache was admitted to the hospital. After detection of a tumoral lesion with an ulcerated surface in stomach during the upper gastrointestinal tract endoscopic examination, the patient underwent surgery. During the operation, multiple nodular lesions were observed in the serosal surfaces of the small intestine and stomach. Gastrectomy and partial small intestine resection specimens were evaluated and the patient was diagnosed as signet ring cell carcinoma in the stomach, and multiple gastrointestinal stromal tumors in the serosal surfaces of both the stomach and small intestine. Resection specimens of patients with GIST need to be evaluated carefully on macroscopic examination, considering the possible presence of a coexistent tumoral lesion.