This study used data from the 1982 Pelotas Birth Cohort Study, Brazil, to estimate the controlled direct effect of early-life socioeconomic position (SEP) on periodontitis at age 31 years, controlling for adulthood income and education, smoking, and dental hygiene. Sex was included as a covariate. Early-life SEP was measured at participant birth based on income, health services payment mode, maternal education, height, and skin color (lower versus middle/higher SEP). Periodontitis was assessed through clinical examination at age 31 years (healthy, mild periodontitis, or moderate-To-severe disease). Adulthood behaviors (smoking, dental hygiene) were the mediators, and adulthood SEP (education and income) represented the exposure-induced mediator-outcome confounders. A regression-based approach was used to assess the controlled direct effect of early-life SEP on periodontitis. Multinomial regression models were used to estimate risk ratios and their 95% confidence intervals. The prevalences of mild and moderate-To-severe periodontitis were 23.0% and 14.3%, respectively (n = 539). Individuals from the lowest early-life SEP had a higher risk of moderate-To-severe periodontitis controlled for mediators and exposureinduced mediator-outcome confounders: risk ratio = 1.85 (95% confidence interval: 1.06, 3.24), E value 3.1. We found that early-life SEP was associated with the development of periodontitis in adulthood that was not mediated by adulthood SEP and behaviors.