Objectives: Antibiotics are too often prescribed in childhood respiratory tract infection (RTI), despite limited effectiveness, potential side effects and bacterial resistance. We aimed to reduce antibiotic prescribing for children with RTI by online training for general practitioners (GPs) and information for parents. Methods: A pragmatic cluster randomized controlled trial in primary care. The intervention consisted of online training for GPs and an information booklet for parents. The primary outcome was the antibiotic prescription rate for children presenting with RTI symptoms, as registered by GPs. Secondary outcomes were number of reconsultations within the same disease episode, consultations for new episodes, hospital referrals and pharmacy-dispensed antibiotic courses for children. This trial was registered at the Dutch Trial Register (NTR), registration number:NTR4240. Results: After randomization, GPs from a total of 32 general practices registered 1009 consultations. An antibiotic was prescribed in 21% of consultations in the intervention group, compared with 33% in the usual care group, controlled for baseline prescribing (rate ratio 0.65, 95% CI 0.46-0.91). The probability of reconsulting during the same RTI episode did not differ significantly between the intervention and control groups, and nor did the numbers of consultations for new episodes and hospital referrals. In the intervention group antibiotic dispensing was 32 courses per 1000 children/year lower than the control group, adjusted for baseline prescribing (rate ratio 0.78, 95% CI 0.66-0.92). The numbers and proportion of second-choice antibiotics did not differ significantly. Conclusions: Concise, feasible, online GP training, with an information booklet for parents, showed a relevant reduction in antibiotic prescribing for children with RTI.