Background & Aim of the Study: The main objective of the Pharmacovigilance programme of India is to create a nationwide system of adverse drug reporting by health care professionals and patients. Nurses are the most essential health care givers who closely monitor the patient health and safety. This study was conducted to assess the Knowledge, Attitude, and Practices (KAP) of Nurses about Pharmacovigilance & Adverse drug reactions (ADR) reporting in tertiary care hospitals in Tamilnadu. Materials and Methods: This is a questionnaire based study with both open and close ended questions on different aspects of Knowledge [6], Attitude [8], and Practice [6] questions. Among 200 OT and ICU Nurses of tertiary care hospitals, 174 responded (87%). KAP among study subjects was measured in Percentages based on their responses. Results: ADR reporting was considered very important by 93.10% of nurses, primarily for improving patient’s safety (69.54%) and identifying new ADRs (57.47%). Majority of nurses (79.88%) opined that all ADRs should be reported, 25.28% are aware about Pharmacovigilance Centre in the hospitals. However, 88.50% said that proper training should be provided to report ADR. Conclusion: The Nurses are aware of ADR reporting and their importance. However, under reporting and lack of knowledge are clearly evident.