Purpose: The aim of this study was to investigate the causative drugs and clinical characteristics of adverse drug reactions (ADR) in children based on electronic self-reporting system in a tertiary university hospital. Methods: The data were retrospectively collected by the spontaneous ADR reporting system within electronic medical record system at Ajou University Hospital from January 2011 to July 2016. ADR of patients aged less than 18 years were included in this study. Results: The total number of ADR cases reported during the study period was 1,886. Excluding “unlikely” cases by causality assessment, 1,852 cases were included in this study. The median age of patients was 7 years (range, 0-17 years) and 60% were male. The most common causative drug was antibiotics (31.0%), followed by antiepileptic drugs (AEDs, 24.4%), opioids (9.4%), and nonsteroidal anti-inflammatory drugs (NSAIDs, 8.3%). Among antibiotics (n=574), ceftriaxone was most common, followed by amoxicillin-clavulanate, ampicillin-sulbactam, and vancomycin. Among AEDs (n=452), valproate was most commonly reported followed by levetiracetam and lamotrigine. Most of opioids-associated ADRs (n=174) were caused by tramadol, and within NSAIDs-associated ADRs (n=154), ibuprofen was the most common causative drug. Cutaneous symptoms (45.3%) were most commonly reported, followed by gastrointestinal (24.9%), and neurologic (14.9%) symptoms. Anaphylaxis was noticed in 1.5% and was most commonly triggered by NSAIDs, followed by antibiotics and anesthetics. Conclusion: Antibiotics were the most common causative drug of ADR in children. Anaphylaxis was noticed in 1.5% and was most commonly triggered by NSAIDs. (This research was supported by a grant from the Ministry of Food and Drug Safety and the Korea Institute of Drug Safety and Risk Management for operation of the regional pharmacovigilance center in 2017.)