Background Due to a large strain on youth mental health care, general practice is suggested as an alternative treatment setting for children and adolescents with anxiety problems. However, research on the current management of these children and adolescents within general practice is scarce. Aim To investigate the incidence of coded anxiety in general practice using the International Classification of Primary Care (ICPC), and GPs' management of children and adolescents presenting with anxiety problems. Design and setting Population-based cohort study using electronic medical records of 51 212 children (aged 0-17 years) in primary care in the Rotterdam region between 1 January 2012 and 31 December 2018. Method Incidence of ICPC codes for anxiety were calculated, then the characteristics of children and adolescents consulting their GP with anxiety and the GPs' management were assessed qualitatively using quantitative content analysis. Results Incidence of ICPC codes for anxiety in children and adolescents was 5.36 (95% confidence interval [CI] = 5.02 to 5.71) per 1000 person- years. Adolescent females had the highest incidence with 14.01 (95% CI = 12.55 to 15.58) per 1000 person-years. Of the 381 children and adolescents consulting their GP with an initial anxiety problem (median age 13.3 years, 40.4% male), GPs referred 59.3% to mental health care in the first year while 26.5% of children and adolescents were managed by a specialised practice nurse within general practice. Of the 381 children and adolescents, 10.5% received psychiatric medication during the first year, with the trend being for increased prescriptions during adolescence. Conclusion In general practice children and adolescents frequently received one of two ICPC codes for anxiety, especially adolescent females. Most presenting to their GP with anxiety problems are referred externally or seen by a specialised practice nurse within general practice.