Aims: To quantify the impact of life course income trajectories on periodontitis in adulthood. Materials and Methods: Data from the 1982 Pelotas Birth Cohort Study, Brazil, were used. Information on family income was collected at birth and ages 15, 19, 23 and 30 years. Group-based trajectory modelling was used to identify income trajectories. Periodontal measures were assessed through clinical examination at age 31. LogPoisson regression models were used to estimate prevalence ratios (PRs) of any and moderate/severe periodontitis, as outcomes. Results: Prevalence of any periodontitis and moderate/severe periodontitis was 37.3% and 14.3% (n = 539). Income trajectories were associated with prevalence of moderate/severe periodontitis. Adjusted PR in participants in low and variable income trajectory was 2.1 times higher than in participants in stable high-income trajectory. The unadjusted association between income trajectories and prevalence of any periodontitis was explained by the inclusion of behavioural and clinical variables in the model. Conclusions: Low and variable life course income increased the prevalence of moderate/severe periodontitis at age 31 years. The findings may inform programmes in identifying and targeting potentially at-risk groups during the life course to prevent periodontitis.