OBJECTIVE: To understand the association of seizure frequency with healthcare resource utilisation (HCRU) and mortality in UK children with epilepsy (CWE). DESIGN: Retrospective cohort study. SETTING: Routinely collected data in primary care from The Health Improvement Network UK database. PATIENTS: CWE >/=1 and<18 years of age with a record of seizure frequency were included in mortality analyses from 2005 to 2015 and HCRU analyses from 2010 to 2015. MAIN OUTCOME MEASURES: Frequency of HCRU contacts during the year following latest seizure frequency and mortality (descriptive and Cox proportional hazards regression) from first record of seizure frequency. RESULTS: Higher seizure frequency was related to increased HCRU utilisation and mortality. In negative binomial regression, each category increase in seizure frequency related to 11% more visits to general practitioners, 35% more inpatient admissions, 15% more outpatient visits and increased direct HCRU costs (24%). 11 patients died during 12 490 patient-years follow-up. The unadjusted HR of mortality per higher category of seizure frequency was 2.56 (95% CI: 1.52 to 4.31). Adjustment for age and number of prescribed anti-epileptic drugs at index attenuated this estimate to 2.11 (95% CI: 1.24 to 3.60). CONCLUSION: Higher seizure frequency is associated with greater HCRU and mortality in CWE in the UK. Improvement in seizure control may potentially lead to better patient outcomes and reduced healthcare use.