This systematic review aimed to evaluate the knowledge of diabetic patients and related factors regarding insulin therapy. A comprehensive search was systematically conducted across several international electronic databases, including Scopus, PubMed, and Web of Science. The search employed Medical Subject Headings (MeSH) keywords including "knowledge", "insulin", and "diabetes", covering records up to May 1, 2024. The quality of the included studies was assessed using the appraisal tool for cross-sectional studies (AXIS tool). A thorough analysis of fourteen cross-sectional studies involving 2,471 diabetic patients revealed an average knowledge level of 56.51 out of 100 regarding insulin therapy. The study identified several significant factors influencing this knowledge level: age, education level, duration of insulin treatment, practical experience, marital status (specifically being single), participation in training courses, urban residence, and male gender. These findings underscore the crucial role of health policymakers and managers in improving diabetic patients’ knowledge of insulin therapy. By targeting interventions toward these specific factors, they can make a significant difference in the lives of diabetic patients.