Gastrointestinal stromal tumors (GISTs) are mesenchymal neoplasms originating from the interstitial cells of Cajal and are the most common sarcomas of the gastrointestinal tract, though rare overall. With over 60% located in the stomach and typically asymptomatic, GISTs may be incidentally encountered during metabolic bariatric surgery, particularly sleeve gastrectomy (SG). Their discovery during routine preoperative workup or intraoperatively presents diagnostic and therapeutic challenges. This chapter provides a structured approach to the pre-, intra-, and postoperative management of GISTs in the context of SG. It includes guidance on the interpretation of endoscopic and endosonographic findings, the role of histopathology, and the relevance of mutational profiling for both diagnostic confirmation and therapeutic planning. Most incidentally discovered GISTs during SG are small, located in the gastric fundus or corpus, and show very low mitotic activity. These lesions have a “very low risk” for recurrence and can typically be resected safely within the planned surgical field without modifying the bariatric approach. Intraoperative biopsy is generally discouraged due to the risk of tumor cell dissemination. Instead, a complete resection with clear margins should be aimed for. Often, postoperative histological evaluation of the gastric specimen is the point of diagnosis. Follow-up recommendations depend on risk stratification. Very-low-risk tumors require no oncologic follow-up beyond routine bariatric care, whereas higher-risk tumors may necessitate adjuvant therapy and surveillance in specialized sarcoma centers. The incidental detection of GISTs during SG represents a rare but manageable scenario when embedded in a multidisciplinary care framework.