Abstract Background Health behaviors in adolescence could have a life-long effect on cardiometabolic health and differ by parental socioeconomic conditions. Adopting a life course perspective and a causal inference framework, we aimed to quantify the differential effect of adolescent unhealthy behaviors on adult cardiometabolic conditions by parental financial situation. Methods Using the National Longitudinal Study of Adolescent to Adult Health in the United States (n = 3,772), we estimated conditional causal effect by parental financial situation through inverse probability-weighted marginal structural models. Exposures were adolescent health behaviors (dietary habits, cigarette smoking, alcohol consumption and physical activity) and the effect modifier was parental financial situation (difficulty paying bills vs. no difficulty), both measured at ages 12-19 (1994-1995). Outcomes were cardiometabolic conditions (hypertension, stroke, cardiac failure, diabetes, chronic kidney disease), measured at ages 33 - 43 (2016-2018) using biomarkers and self-reports. Results There were 1,206 participants with cardiometabolic conditions after 20 years of follow-up. Alcohol consumption among adolescents with parental financial difficulty led to 325 more cardiometabolic cases (95% confidence interval: 2 - 647) compared to alcohol consumption by their peers without financial difficulty. This differential effect is driven more by cardiovascular conditions (hypertension, stroke, or cardiac failure) than by metabolic conditions (diabetes or chronic kidney disease). There were no differential effects of dietary habits, cigarette smoking and physical inactivity on the occurrence of adult cardiometabolic conditions. Conclusions Public health initiatives targeting alcohol consumption during adolescence could mitigate socioeconomic inequalities in adult cardiometabolic conditions. Key messages • Socioeconomically disadvantaged adolescents are more susceptible to the long-term detrimental health effects of alcohol consumption. • These susceptible groups may need targeted interventions to mitigate the cardiometabolic effect of alcohol consumption.