Background/Objectives: Diabetes is frequent among cancer patients. Diabetes and cancer co-occurrence may result in a worse prognosis and complications in cancer patients. This systematic review aims to investigate the impact of glycemic control in patients having both cancer and diabetes. Methods: PubMed, Web of Science, Science Direct, and Google Scholar were systematically searched to include the relevant literature. Rayyan QRCI was used throughout this systematic approach. Results/ Interpretation: A total of thirteen studies with 13550 patients were included in this review. The reported follow-up duration ranged from 2 to 12 months. Cancer patients with diabetes are more likely to get infections, be hospitalized, and require chemotherapy reductions or discontinuation. Having cancer with comorbid diabetes affects diabetes self-management and results in poor glycemic control. Applying clinical pharmaceutical programs to raise awareness about compliance with diabetic medication along with cancer treatment was found to have positive outcomes. Evidence-based practice recommendations or policies should be developed that advocate assessing diabetes patients' glycemic state at the time of cancer diagnosis.