Aims Healthcare workers’ (HCWs) ability to recognize, classify and manage adverse reactions (ADR) is crucial to ensure patient safety. This study assessed HCWs’ awareness, knowledge, and practice on ADR. Methods This was a cross sectional online questionnaire case-based study, involving clinical HCWs at two tertiary hospitals. Results We recruited 321 respondents with 256 doctors, 58 nurses and seven medical assistants. HCWs with more than five years’ experience and dermatologists had better ADR knowledge. Three-quarter failed to recognize off-target nonimmune mediated non-steroidal anti-inflammatory drugs reactions. About 26% (n=84) could not recognize severe cutaneous adverse drug reactions (SCARs). In those who recognized SCARs, only 76.6% (n=177) will not re-introduce the implicated drugs. Knowledge in managing anaphylaxis and awareness in paradoxical drug-induced reaction was poor. About 18% (n=58) did not use adrenaline in anaphylaxis and 80% (n=259) were unfamiliar with the usefulness of tryptase in anaphylaxis. Nearly 52% were ignorant of succinylated gelatin solution as a hidden allergen. Nearly 90% (n=286) were unfamiliar with utilization of fresh frozen plasma in severe ACE-inhibitor induced angioedema. A significant proportion of respondents understood the reporting pathway for ADRs to medications and vaccines, respectively. Only up to 67.3% (n=216) understood the need to update ADR reporting when a new reaction occurred. Conclusion The overall HCWs knowledge and practice on ADRs is not satisfactory where they lacked awareness on many aspects of ADRs. These findings provide supportive evidence for the incorporation of ADR into the healthcare curricula and plan periodic programs to ensure patient safety.