Background: Children are more susceptible to medication errors and adverse reactions. In addition, variation in body mass and medication discrepancies are the major causes of medication errors, which pose a risk of harm to children. When unresolved, these issues can lead to longer hospital stays, increased hospital readmissions, and emergency room care that burden the healthcare system. Many organizations have struggled to implement medication reconciliation. In this context, studies demonstrated that reliability and improvement science methods can be used to implement a successful and sustained medication reconciliation process. One of the initial steps involved in medication reconciliation process is determining the sector for implementation. Therefore, the aim of this study was to determine the prevalence of medication discrepancies occurring throughout the course of a hospital stay and describe the types of discrepancies and medications most commonly involved in pediatric cases. Methods: A cross-sectional study was carried out from July 2017 to March 2018 in the pediatric department of a high-complexity public hospital in Brazil. Data collection consisted of: collection of sociodemographic data, clinical interview with the patient's caregiver, registration of patient prescriptions, and evaluation of medical records. Discrepancies were classified as intentional or unintentional and included omission of medication, therapeutic duplicity, different dose, frequency, route of administration than prescribed. Study approved by the Research Ethics Committee (CAAE: 36927014.4.0000.5546). Results: During care transitions, 114 children were followed. Patients presented unintentional discrepancies, of which 16 (14.0%) presented discrepancies at hospital admission, 42 (36.8%) during ward transfer, and 52 (45.6%) during discharge. Omission represented 74% (n=20) ofthe errors at admission, 38% (n=26) at ward transfer, and 100% (n=80) at discharge. The most frequent discrepancies in the three transitions were related to antimicrobials, representing 43.3% of discrepancies at admission, 38.8% at internal transfer, and 61.2% during discharge. Conclusion: The results demonstrated that the main transition levels when unintentional discrepancies occurred in children in this hospital were during internal transfer and discharge and indicated difficulties in interprofessional communication and poor documentation. Evaluation of all transition points is essential for determining the most critical point in the quality of care provided at hospitals.