Sunitinib an inhibitor of the vascular endothelial growth factor receptor, is highly effective against renal cell carcinoma and is now widely used in patients with metastatic disease. Gastroesophageal reflux disease (GERD) is rarely reported as a side effect of sunitinib. We report two cases of GERD with upper gastrointestinal bleeding related to sunitinib administration. Both cases responded well to conservative management. Microscopic findings in both cases showed cellular atypia such as hyperchromasia, increases in nuclear size, and multinucleation. The cellular atypia of the squamous mucosa appears to be associated with reparative processes.