BACKGROUND: Medication administration in busy emergency departments (EDs) presents significant challenges due to the high-pressure environment and complexity of processes. Medication administration errors (MAEs) are a critical concern as they can severely impact patient safety and increase healthcare costs. Understanding the prevalence and underlying factors contributing to intravenous MAEs is essential for enhancing patient care and improving hospital services. This study aims to explore and measure the frequency of intravenous MAEs in EDs and identify factors contributing to these errors during their preparation and administration. METHODS: This prospective study utilized the direct observation technique where the preparation and administration of 222 intravenous medications were observed in the EDs of two hospitals in Malaysia. Information on medication preparation, administration, and other procedures was recorded. Error rates were calculated, and multivariable logistic regression was conducted to identify factors contributing to intravenous MAEs. RESULTS: MAEs were detected in 83.3% (185/222) of the observed medications affecting 86.7% (124/143) patients. Among these, a total of 240 MAEs were identified, with the most common being wrong rate of administration (55.8%), wrong preparation technique (20.8%), and omission error (11.7%). Alimentary tract and metabolism medications accounted for the highest proportion of MAEs (52.0%), followed by anti-infective medications (21.7%) and nervous system medications (15.4%). Excluding wrong time errors reduced the error rate to 80.2% (178/222). Nonverbal orders and inadequate or absence of labelling were significantly associated with MAEs, while factors such as the complexity of preparations, working shift, experience, and high-alert medications showed no significant associations. CONCLUSION: The study highlighted a high prevalence of intravenous MAEs in EDs. Nonverbal orders and inadequacy in labelling of medications were significant contributing factors to MAEs in the ED. Implementing an admixture labelling policy, comprehensive training programmes, strict enforcement of existing guidelines and protocols through regular audits, establishing nonpunitive error reporting system, and technological solutions where financially feasible are crucial for mitigating these errors to promote patient safety.