Background: Cardiovascular medications have been commonly associated with medication errors. Objective: The objective of this study was to investigate the incidence and predictors of medication errors in patients with acute coronary syndrome. Setting: the coronary care unit of a university teaching hospital. Methods: This was a prospective observational study on 150 patients admitted to the coronary care unit between August 2014 and July 2015. Main outcome measure: The principal outcome was the number (frequency) of encountered medication errors. Results: Of total 5790 prescription items reviewed, 547 (9.4%) potential medication errors were identified of which 523 (9.0%) were prescribing errors and 24 were monitoring errors. The most frequent prescribing errors were dosing errors (231, 42.2%) followed by loading dose omission error (91, 16.6%), omission of essential drugs on 1st day(43, 7.9%), and timing error (40, 7.3%). Errors frequently encountered with drugs such as aspirin, enoxaparin, beta-blockers followed by angiotensin-converting enzyme inhibitors and clopidogrel. Multivariate logistic regression analysis revealed that renal impairment (OR 6.02; 95% CI1.4–35.4; p = 0.02) and longer duration of hospital stay (OR 4.01; 95% CI 1.5–10.7; p = 0.005) were predictors of the higher incidence of medication errors. Conclusion: Prescribing and monitoring errors in coronary care unit are frequent and avoidable, with the majority of errors were ranked to be of mild to moderate severity. Dosing errors, omission of essential drugs and monitoring errors were most common error types encountered. Dosage adjustment based on estimation of the glomerular filtration rate immediately after admission help avoiding dosage-related errors.