Clinical Decision Support Systems (CDSSs) has been developed for utilization to provide rational therapy to Diabetes Mellitus (DM) patients including preventing Drug-related Problems (DRPs) such as the effect of drug treatment being not optimal, untreated indications and symptoms, unnecessary therapy, and adverse drug reactions. This study aims to summarize the available evidence on the intervention of CDSSs, key outputs, and impact of the user in DM patients. This study was a systematic review using PubMed, Scopus database, and by manually searching the bibliographies of articles that have been found. We included studies reporting on evaluated CDSSs that had been implemented in medication prescription, reducing medication errors, adverse drug events, drug-allergy checking, drug dosing support, and so on. A total of 8 studies were selected among 855 studies. CDSSs are used in hospitals and primary care settings to identify potential drug interactions, correct therapy regimens, monitor therapy, blood glucose documentation, ensure patients receive medication according to the guideline, provide nutritional advice, and schedule physical activity. The usage of CDSSs improves blood glucose levels, detects possible drug interactions, reduces face-to-face consultations, improves documentation, assists in identifying dose, and promotes prescribing in line with the guideline. The use of CDSSs can help to reduce the risk of errors in management therapy.