Adverse drug reaction (ADR) reporting is fundamental in the science of pharmacovigilance. However, underreporting still exists and remains a major limitation of the system. This study sought to assess the knowledge and attitudes of hospital-based health practitioners in Manila towards adverse drug reaction reporting. A convenience sampling method was used among health professionals in selected hospitals in Manila. Data was collected using selfadministered questionnaires from randomly selected pharmacists (23), physicians (47) and nurses (70). Results indicated that there is under-reporting of suspected ADRs. Majority of the health professionals (77%) have adequate knowledge on the ADR reporting. However, there is a significant difference on the level of knowledge of these practitioners. Nurses have the highest proportion of respondents (86%) with adequate knowledge. In addition, a higher percentage of respondents (80%) have unfavorable attitude towards ADR reporting. But still, the respondents acknowledged that ADR reporting is a professional obligation. Only years of practice in the profession appeared to possess a significant relationship to the practitioners’ knowledge. Meanwhile, only history of ADR reporting exhibited a significant influence to the attitudes of health practitioners. Those who had experienced reporting ADR are more likely to report ADRs. Knowledge and attitudes showed a strong influence in the ADR reporting of health professionals. Thus, development of education strategies which focused on recognition of ADRs as well as altering wrong beliefs and negative attitudes will hopefully develop a “reporting and learning culture” among the health professionals.