Introduction: Diabetes mellitus is a metabolic disease which is a major health care issue in geriatric population of Southeast Asian countries. Inappropriate prescriptions and polypharmacy are important prescribing issues with diabetic geriatric patients due to its associated co-morbid conditions. Beers criteria and WHO core indicators are developed for the rational use of drugs in this specific population. The incidences of potentially inappropriate medications (PIMs) are reduced by following the appropriate guidelines for the elderly patients. The aim and objectives of this study were to estimate the prevalence of potentially inappropriate medications using the Beers criteria and also to assess the prescribing pattern for geriatric outpatients diagnosed with diabetes mellitus. Methodology: The study is a prospective and cross-sectional in nature, consisting of geriatric patients (65 years and above) attending the medicine outpatients clinic of a tertiary care teaching hospital. The drug utilization aspects of the study were assessed by World Health Organization guidelines (WHO) and American Geriatric Society 2015 updated Beers criteria for drug-use indicators and incidence of potentially inappropriate medications, respectively. Results and Discussion: Medical records of 250 patients aged 65 years and above were assessed for this study. Nearly 52 patients were diagnosed with diabetes mellitus and its associated complication. A number of drugs prescribed to the patients were 436 with an average of 8.4 drugs per person. Cardiovascular drugs accounted for most (35.09%) followed by anti-diabetic drugs (31.88%) and multivitamins (11.92%). Potentially inappropriate medications were prescribed to 23 patients with a rate of 8.25% when reviewed with Beers Criteria 2015 by the American Geriatric Society. The common groups involved in PIMs were mostly benzodiazepines and anti-depressants. Conclusion: Potentially inappropriate medications and polypharmacy are major pharmacotherapeutic issues which go unnoticed especially in a country like India. This might be due to the shortage of doctors, lack of knowledge regarding PIMs, drug interaction and polypharmacy. There is a need for training of rational use of medicine among prescriber serving the geriatric population of the country.