Context: Patient harm resulting from medication errors drives prevention efforts, yet harm associated with medication errors in children has not been systematically reviewed. Objective: To review the incidence and severity of preventable adverse drug events (pADEs) resulting from medication errors in pediatric inpatient settings. Data sources: Data sources included Cumulative Index of Nursing and Allied Health Literature, Medline, Scopus, the Cochrane Library, and Embase. Study selection: Selected studies were published between January 2000 and December 2017, written in the English language, and measured pADEs among pediatric hospital inpatients by chart review or direct observation. Data extraction: Data extracted were medication error and harm definitions, pADE incidence and severity rates, items required for quality assessment, and sample details. Results: Twenty-Two studies were included. For children in general pediatric wards, incidence was at 0 to 17 pADEs per 1000 patient days or 1.3% of medication errors (of any type) compared with 0 to 29 pADEs per 1000 patient days or 1.5% of medication errors in ICUs. Hospital-wide studies contained reports of up to 74 pADEs per 1000 patient days or 2.6% of medication errors. The severity of pADEs was mainly minor. Limitations: Limited literature on the severity of pADEs is available. Additional study will better illuminate differences among hospital wards and among those with or without health information technology. Conclusions: Medication errors in pediatric settings seldom result in patient harm, and if they do, harm is predominantly of minor severity. Implementing health information technologies was associated with reduced incidence of harm.