OBJECTIVES: Irrational use of antibiotic, which adds to the cost of treatment, is known to lead to resistant microorganisms. Antimicrobial resistance substantially adds the already high costs of healthcare; and, it increases patient morbidity and mortality. Aim of the present study is to compare antimicrobial utilization in Cardiac Intensive Care Unit (CCU) and Medical Intensive Care Unit (MICU) of a private tertiary care hospital.  METHODS: This study was carried out in CCU and MICU of a private tertiary care hospital. The data on antimicrobial utilization was collected prospectively from CCU and MICU. The antimicrobial utilization pattern was assessed using Rational Pharmaceutical Management (RPM) indicators. RESULTS: A total of 325 patients’ data was analyzed in CCU and MICU (229 & 96, respectively). The average number of AMAs prescribed was found to be 1.8±0.06. The average number of AMAs prescribed in MICU (2.6±0.16) was higher than that prescribed in CCU (1.8±0.06). AMAs contributed to the extent of 14% and 21% of the total drugs prescribed in CCU and MICU, respectively. Cefuroxime, Ceftriaxone, Vancomycin, and Piperacillin+Tazobactum were the most commonly prescribed AMAs in CCU, while Penems, antifungals, Ceftriaxone, Piperacillin+Tazobactum and Metronidazole were the commonly prescribed AMAs in MICU. Of 586 AMAs prescribed in both the ICUs, 31.5% AMAs were prescribed from the National List of Essential Medicines 2011, India (NLEM-2011). 96/338 AMAs were prescribed in CCU and 89/248 in MICU from NLEM-2011. Only 4.3% of AMAs were prescribed by generic name. A total of 67% of parenteral AMAs were prescribed, of which 53% from CCU (338) and 85% from MICU (248). CONCLUSIONS: On the basis of RPM indicators computed in this study, there is a need to consolidate these early findings.