||Most of the time discharge from the hospital after hospitalization involves disturbance of care, multiple changes in medications and medication regimens, and insufficient patient education, which can cause several adverse drug events (ADEs) and unnecessary health care utilization that can be avoided. The objective of this study is to determine the impact of clinical pharmacist intervention on decreasing the incidence of preventable ADEs after patient discharge. A randomized trial was conducted involving 250 patients being discharged from the general medicine service at a large teaching hospital in Cairo (Egypt). Patients in the intervention group received pharmacist counseling at discharge and a follow-up telephone call 3 to 4 days later. Intervention group counseling concentrates on reviewing indications, clarifying medication regimens; explaining directions of use, explaining potential side effects of medications; screening for barriers to adherence; and providing patient counseling. Patients in the control group received the standard dispensing and counseling with no follow-up telephone call. The primary outcome was the rate of preventable ADEs. All patients in the trial were contacted 30 days after discharge to assess adherence and the occurrence of ADE. Clinical pharmacists observed that medication non-adherence happened in about 13%.of the intervention group versus 24% in the control group (P-value < 0.05). Comparing study outcomes 30 days after discharge, preventable ADEs were detected in 14% of patients in control group and 3% of patients in intervention group (P-value<0.05). Clinical pharmacists’ interventions such as medication review, patient counseling, and telephone follow-up were associated with a statistically significant lower rate of preventable ADEs 30 days after hospital discharge (P-value <0.05) through reduction in medication discrepancies and improvement of adherence to medication regimen. Greater roles for clinical pharmacists in hospital care should be considered, especially in case of patient at high risk to ADE and poor compliance.