Aim: To evaluate the effect of sorafenib on the glucose tolerance and diabetic status of patients with metastatic renal cell carcinoma (RCC) or advanced hepatocellular carcinoma (HCC). Materials & methods: Eighty patients with metastatic RCC or advanced HCC received 400 mg sorafenib twice daily for an average of approximately 8 and 5 months, respectively; 22 had diabetes mellitus and three had prediabetes. Results: One of 55 nondiabetic patients, and one of three patients with impaired fasting glucose or impaired glucose tolerance developed diabetes mellitus, one of 12 patients on oral antihyperglycemic agents switched to insulin and no patient treated with insulin needed to increase their dose. Conclusion: Sorafenib has the potential to be a feasible and safe treatment option for patients with advanced HCC or metastatic RCC and comorbid diabetes mellitus or prediabetes.