Introduction and Aims. Results from previous research are inconsistent regarding the association between socioeconomic status (SES) and cannabis use among adolescents. Since there are risks associated with cannabis use, a social gradient in cannabis use may contribute to reproducing socioeconomic differences in life opportunities. The aim of this study was to assess the association between childhood SES and cannabis use among youth in Sweden. Design and Methods. We used repeated cross‐sectional data from three waves (2014–2016) of the Swedish national school survey among 11th graders. The analysis encompassed 9497 individuals in 668 school classes. Childhood SES was measured through parents' highest education, as reported by the students. Cannabis use was measured in terms of lifetime use and frequency of use. Data were analysed using multi‐level mixed‐effects Poisson regression. Results. Adolescents with at least 1 parent with university/college education had 17% (incidence rate ratio 1.17, confidence interval 1.05, 1.30) higher risk of lifetime use of cannabis compared with those whose parents had no university/college education, adjusting for sex, SES of the school environment, academic orientation, truancy, risk assessment and parental permissiveness. Among life‐time users of cannabis, risk for frequent cannabis use was 28% (incidence rate ratio 0.72, confidence interval 0.53, 0.97) lower for those with at least 1 parent with university or college education. Discussion and Conclusions. Childhood SES, in terms of parental education, was associated with cannabis use among Swedish adolescents. Adolescents from families with lower SES were less likely to ever try cannabis, but at higher risk for frequent use.