Muath Fahmi Najjar,1,2 Syed Azhar Syed Sulaiman,2 Majed Al Jeraisy,1 Hashim Balubaid3 1King Abdullah International Medical Research Centre, King Saud bin Abdulaziz University for Health Science, College of Pharmacy, King Abdulaziz Medical City, Ministry of National Guard-Health Affairs, Riyadh, Saudi Arabia; 2Pharmaceutical Sciences School, Clinical Pharmacy Discipline, Universiti Sains Malaysia, Penang, Malaysia; 3King Abdullah International Medical Research Centre, King Saud bin Abdulaziz University for Health Science, College of Medicine, King Abdulaziz Medical City, Ministry of National Guard-Health Affairs, Riyadh, Saudi Arabia Background: There is a difference between evidence-based guidelines for geriatric patients and clinical practice of physicians. Prescribing potentially inappropriate medications (PIMs) can be attributed to the fact that many physicians are not aware of PIMs usage. Aim: The aim of this study was to assess the effectiveness of a combined intervention program comprising an educational and clinical pharmacist intervention to reduce the incidence of PIMs among hospitalized geriatric patients. Methods: This was a prospective pre-test versus post-test design study. The screening tool of older persons’ prescriptions, 2nd version, and 2015 American Geriatric Society Beers’ criteria were used to assess the appropriateness of medications prescribed for geriatric inpatients. The study was carried out in the medical wards of the Department of Medicine at King Abdulaziz Medical City in Riyadh, Saudi Arabia. Results: Four hundred geriatric patients were enrolled in the study: 200 in a pre-intervention group (control) and 200 in the intervention group. After the combined intervention, the incidence rate of PIMs decreased significantly from 61% to 29.5% (p<0.001). Out of 317 recommendations given by the clinical pharmacist, the physicians accepted a total of 196 (61.83%) recommendations. The most common PIMs to avoid regardless of diagnosis of geriatric patients before interventions were first-generation antihistamines (46%), sliding scale insulin (18.5%), antipsychotics (6.5%), benzodiazepines (9.5%), and antiarrhythmic drugs (15%). Conclusion: Using a combined intervention program that comprises an educational intervention of updated evidence-based guidelines and clinical pharmacist intervention would add a significant value to improve prescribing patterns in hospitalized geriatric patients. Keywords: education, inappropriate, medication, elderly, Beers criteria, STOPP criteria