Background Medication reconciliation has been mandated by the Irish government at transfer of care. Research is needed to determine the contribution of clinical pharmacists to the process. Objective To describe the contribution of emergency department based clinical pharmacists to admission medication reconciliation in Ireland. Main Outcome Measure Frequency of clinical pharmacist’s activities. Setting Two public university teaching hospitals. Methodology Adults admitted via the accident and emergency department, from a non-acute setting, reporting the use of at least three regular prescription medications, were eligible for inclusion. Medication reconciliation was provided by clinical pharmacists to randomly-selected patients within 24-hours of admission. This process includes collecting a gold-standard pre-admission medication list, checking this against the admission prescription and communicating any changes. A discrepancy was defined as any difference between the gold-standard pre-admission medication list and the admission prescription. Discrepancies were communicated to the clinician in the patient’s healthcare record. Potentially harmful discrepancies were also communicated verbally. Pharmacist activities and unintentional discrepancies, both resolved and unresolved at 48-hours were measured. Unresolved discrepancies were confirmed verbally by the team as intentional or unintentional. A reliable and validated tool was used to assess clinical significance by medical consultants, clinical pharmacists, community pharmacists and general practitioners. Results In total, 134 patients, involving 1,556 medications, were included in the survey. Over 97 % of patients (involving 59 % of medications) experienced a medication change on admission. Over 90 % of patients (involving 29 % of medications) warranted clinical pharmacy input to determine whether such changes were intentional or unintentional. There were 447 interventions by the clinical pharmacist regarding apparently unintentional discrepancies, a mean of 3.3 per patient. In total, 227 (50 %) interventions were accepted and discrepancies resolved. At 48-hours under half (46 %) of patients remained affected by an unintentional unresolved discrepancy (60 % related to omissions). Verbally communicated discrepancies were more likely to be resolved than those not communicated verbally (Chi-square (1) = 30.029 p < 0.05). Under half of unintentional unresolved discrepancies (46 %) had the potential to cause minor harm compared to 70 % of the resolved unintentional discrepancies. None had the potential to result in severe harm. Conclusion Clinical pharmacists contribute positively to admission medication reconciliation and should be engaged to deliver this service in Ireland.