Background: Assessment of prescribing patterns is an important approach to evaluate the quality of healthcare delivery and promote rational drug use. The World Health Organization (WHO) prescribing indicators serve as standardized tools to assess drug utilization practices in healthcare settings. Objective: To analyze drug prescribing patterns in the outpatient department (OPD) of a tertiary care hospital in Thiruvallur using WHO core prescribing indicators. Methods: A prospective, cross-sectional observational study was conducted in the OPD over a two-month period (February–March 2024). A total of 665 randomly selected prescriptions were evaluated using WHO prescribing indicators. Data were compiled in Microsoft Excel 2021 and analyzed using descriptive statistics. Results: A total of 2,628 drugs were prescribed, with a mean of 3.94 drugs per encounter, indicating polypharmacy. Generic prescribing was observed in approximately 90% of drugs, and 98% were from the WHO Essential Drugs List. Antibiotics were prescribed in 35% of encounters, while injections accounted for 3%. Amoxicillin was the most frequently prescribed antibiotic, mainly for respiratory tract infections. Vitamin supplements and antiulcer drugs were the most commonly prescribed therapeutic classes. Conclusion: The study demonstrates appropriate practices regarding the use of essential medicines and injections. However, the higher average number of drugs per prescription and antibiotic use highlight the need for interventions aimed at reducing polypharmacy and promoting rational antibiotic prescribing. Background: Assessment of prescribing patterns is an important approach to evaluate the quality of healthcare delivery and promote rational drug use. The World Health Organization (WHO) prescribing indicators serve as standardized tools to assess drug utilization practices in healthcare settings. Objective: To analyze drug prescribing patterns in the outpatient department (OPD) of a tertiary care hospital in Thiruvallur using WHO core prescribing indicators. Methods: A prospective, cross-sectional observational study was conducted in the OPD over a two-month period (February–March 2024). A total of 665 randomly selected prescriptions were evaluated using WHO prescribing indicators. Data were compiled in Microsoft Excel 2021 and analyzed using descriptive statistics. Results: A total of 2,628 drugs were prescribed, with a mean of 3.94 drugs per encounter, indicating polypharmacy. Generic prescribing was observed in approximately 90% of drugs, and 98% were from the WHO Essential Drugs List. Antibiotics were prescribed in 35% of encounters, while injections accounted for 3%. Amoxicillin was the most frequently prescribed antibiotic, mainly for respiratory tract infections. Vitamin supplements and antiulcer drugs were the most commonly prescribed therapeutic classes. Conclusion: The study demonstrates appropriate practices regarding the use of essential medicines and injections. However, the higher average number of drugs per prescription and antibiotic use highlight the need for interventions aimed at reducing polypharmacy and promoting rational antibiotic prescribing.