Background: Early hospital readmission of patients after discharge is a public health problem. One major cause of hospital readmission is dysfunctions in integrated pathways between community and hospital care that can cause adverse drug events. Furthermore, the French ENEIS 2 study showed that 1.3% of hospital stays originated from serious adverse drug events in 2009. Pharmacy-led medication reviews at hospital transitions are an effective means of decreasing medication discrepancies when conducted at admission or discharge. However, it is difficult to assess the true impact of pharmacist-led medication reviews in specific high-risk populations, such as pediatric and geriatric populations. In such a context, it is important to demonstrate the effectiveness of medication reconciliation as part of a standardized medication review process—in pediatric and elderly populations—on all-cause readmissions in a large randomized controlled clinical trial. The aim of this study is to assess the impact of the pharmacist-led medication review on the rate of readmissions and/or death after hospital discharge and patient treatment satisfaction.