AbstractAimEstimate the incidence of asthma among children aged 0 to 15 years in Denmark, Finland, Norway and Sweden during 2000–2017.MethodsCases of preschool asthma (up to 6 years) and school‐age asthma (from 6 years) were identified through national registers using an algorithm including hospital diagnoses and prescription medicines. The respective cumulative incidence (CI) was estimated in 1‐year age intervals for each country and birth year.ResultsThe CI of algorithm‐based preschool asthma peaked for the birth cohorts 2008 or 2009 at 14.8% in Denmark, 11.0% in Finland, 15.1% in Norway and 13.7% in Sweden. For later birth cohorts, a slight decrease was observed. The CI of school‐age asthma was 7.1% in Denmark, 10.5% in Finland, 9.7% in Norway and 10.2% in Sweden (children born in 2002). A slight decline over time was seen in Denmark and Norway, and a slight increase in Sweden and Finland.ConclusionFinland had a markedly lower CI of preschool asthma and Denmark lower CI of school‐age asthma as estimated by prescriptions and hospital diagnoses. Preschool asthma may have plateaued in the Nordic countries. For school‐age asthma trends over time varied by country. Differences in diagnostic and prescription practices may have influenced the results.