Diabetes and cancer are common chronic diseases worldwide, and emerging evidence highlights a strong connection between them. Epidemiological studies have suggested a link between diabetes mellitus and certain types of cancer. The risk of developing various forms of diabetes appears to increase in individuals with cancer. Conversely, some cancers and their treatment may lead to the onset of diabetes mellitus. Several factors contribute to the relationship between diabetes and cancer, including genetic predisposition, obesity, inflammation, hyperglycemia, cancer therapies, insulin levels, oxidative stress, and certain oral hypoglycemic medications. Understanding the complex interplay between these diseases is necessary to develop targeted prevention and treatment strategies. This chapter discusses the metabolic connections between cancer and diabetes and outlines the underlying mechanisms involved. It concludes by emphasizing the importance of an integrated, multidisciplinary approach to managing patients with both diabetes and cancer to improve overall patient outcomes.