Aim To evaluate the impact of an emergency department (ED) pharmacist on prescribing errors 24 hours post‐admission. Method A prospective controlled sequential study was conducted in the ED of a metropolitan teaching hospital. In the control period, ED patients admitted were followed‐up by ward pharmacists (standard practice). In the active period, they were seen first by the ED pharmacist. Targets of 50 patients were recruited into each study period. All medication charts were reviewed by a senior clinical pharmacist (reviewing pharmacist) at 24 hours post‐admission. Errors were risk‐assessed by a blinded independent physician. The number and type of errors were compared. Results The profile, type and complexity of patients and number of medications ordered per patient were similar in both periods. There was a 71% relative reduction in errors per patient (p < 0.0001) and a 76% relative reduction in errors per drug order (p < 0.0001) between the control and active periods. The number of errors rated as high‐extreme, moderate or minor, decreased by 64%, 71% and 90% respectively. Overall, the most common types of error were drug omissions (63%); and the most common drugs involved were cardiovascular (31.5%), central nervous system (18%), respiratory (12.6%) and endocrine (10.8%). Conclusion An ED pharmacist providing timely medication histories resulted in admitted patients significantly more likely to receive an accurate medication chart early in their hospital stay.