We aimed to evaluate antiepileptic drug treatment persistence and adherence in paediatric epilepsy patients and investigate the association between medication‐taking behaviours and clinical outcome. Methods. Medical and prescription records of newly treated paediatric epilepsy patients, aged 1–18 years who initiated antiepileptic drug monotherapy in a tertiary teaching hospital, were retrospectively reviewed. The rates of overall treatment, non‐persistence, a treatment gap >60 days, and adherence, as measured by a medication possession ratio ≥0.8, were assessed. The relationship between non‐adherence and clinical outcome, defined as an emergency department visit or hospitalisation due to seizure‐related reasons, was analysed. Results. A total of 1,172 patients met the inclusion criteria. The proportion of patients who were both persistent and adherent at one year was 70.14% and decreased to 56.83% at two years. Patients who started an antiepileptic drug at one year of age, took older generation antiepileptic drugs as the initial treatment, and those diagnosed with localized seizures were less likely to be adherent to and persistent with overall antiepileptic drug treatment. Patients who were non‐adherent to antiepileptic drug treatment were at an increased risk of hospitalisation or emergency department visits for seizure‐related reasons (adjusted HR 2.10, 95% CI 1.25–3.55). Conclusions. This large population study shows that 70% of paediatric epilepsy patients were persistent with and adherent to antiepileptic drugs after one year of treatment and confirms that non‐adherence to antiepileptic drug treatment is an important factor in seizure‐related clinical outcome.