Objectives Evidence regarding the prevalence of medication prescribing errors (PEs) and potential factors that increase PEs among patients treated in the emergency department (ED) are limited. This study aimed to explore the prevalence and nature of PEs in discharge prescriptions in the ED and identify potential risk factors associated with PEs. Methods This was a prospective observational cross-sectional study in an ambulatory ED in a tertiary teaching hospital. Data were collected for six months using a customized reporting tool. All patients discharged from ED with a discharged prescription within the study period were enrolled in this study. Results About 13.5% (n = 68) of the 504 prescriptions reviewed (for 504 patients) had at least one error. Main PEs encountered were wrong dose (23.2%), wrong frequency (20.7%), and wrong strength errors (14.6%). About 36.8% of identified PEs were related to pediatric prescriptions, followed by the acute care emergency unit (26.5%) and the triage emergency unit (20.6%). The main leading human-related causes associated with PEs were lack of knowledge (40.9%) followed by an improper selection from a computer operator list (31.8%). The leading contributing systems related factors were pre-printed medication orders (50%), lack of training (31.5%), noise level (13.0%), and frequent interruption of prescriber and distraction (11.1%). Prescribers' involved with the identified errors were resident physicians (39.4%), specialists (30.3%), and (24.4%) were made by general practitioners. Physicians rejected around 12% of the pharmacist-raised recommendations related to the identified PEs as per their clinical judgment. Conclusion PEs in ED setting are common, and multiple human and systems-related factors may contribute to the development of PEs. Further training to residents and proper communication between the healthcare professionals may reduce the risk of PEs in ED.