BACKGROUND AND OBJECTIVES: Socioeconomic disadvantage throughout the life course is associated with increased risk of cardiometabolic diseases, but traditional risk factors do not fully account for the social gradient. We investigated the interactions between low socioeconomic status (SES) and infection in childhood and adverse cardiometabolic parameters in adulthood. METHODS: Participants from the Cardiovascular Risk in Young Finns Study, a cohort well phenotyped for childhood and adulthood cardiometabolic risk factors and socioeconomic parameters, were linked to lifetime hospitalization data from birth onward available from the Finnish National Hospital Registry. In those with complete data, we investigated relationships between infection-related hospitalization in childhood, SES, and childhood and adult cardiometabolic parameters. RESULTS: The study cohort consisted of 1015 participants (age range 3–18 years at baseline and 30–45 years at follow-up). In adults who were raised in below-median income families, childhood infection-related hospitalizations (at age 0–5 years) were significantly associated with higher adult BMI (β ± SE comparing those with 0 vs ≥1 hospitalizations 2.4 ± 0.8 kg/m2, P = .008), waist circumference (7.4 ± 2.3 cm, P = .004), and reduced brachial flow–mediated dilatation (−2.7 ± 0.9%, P = .002). No equivalent associations were observed in participants from higher-SES families. CONCLUSIONS: Infection was associated with worse cardiovascular risk factor profiles only in those from lower-SES families. Childhood infection may contribute to social gradients observed in adult cardiometabolic disease risk factors. These findings suggest reducing childhood infections, especially in socioeconomic disadvantaged children, may reduce the cardiometabolic disease burden in adults.