Background:DNA methylation at theGFI1-locus has been repeatedly associated with exposure to smoking fromthe foetal period onwards. We explored whether DNA methylation may be a mechanism that links exposure tomaternal prenatal smoking with offspring's adult cardio-metabolic health.Methods:We meta-analysed the association between DNA methylation atGFI1-locus with maternal prenatalsmoking, adult own smoking, and cardio-metabolic phenotypes in 22 population-based studies from Europe,Australia, and USA (n= 18,212). DNA methylation at theGFI1-locus was measured in whole-blood. Multivari-able regression models werefitted to examine its association with exposure to prenatal and own adult smoking.DNA methylation levels were analysed in relation to body mass index (BMI), waist circumference (WC), fastingglucose (FG), high-density lipoprotein cholesterol (HDL—C), triglycerides (TG), diastolic, and systolic blood pres-sure (BP).Findings:Lower DNA methylation at three out of eightGFI1-CpGs was associated with exposure to maternal pre-natal smoking, whereas, all eight CpGs were associated with adult own smoking. Lower DNA methylation atcg14179389, the strongest maternal prenatal smoking locus, was associated with increased WC and BP when ad-justed for sex, age, and adult smoking with Bonferroni-correctedPb0·012. In contrast, lower DNA methylationatcg09935388,thestrongest adultownsmokinglocus, wasassociated with decreasedBMI, WC,and BP (adjusted1×10−7bPb0.01). Similarly, lower DNA methylation at cg12876356, cg18316974, cg09662411, andcg18146737 was associated with decreased BMI and WC (5 × 10−8bPb0.001). Lower DNA methylation at allthe CpGs was consistently associated with higher TG levels.Interpretation:Epigenetic changes at theGFI1were linked to smoking exposurein-utero/in-adulthood and ro-bustly associated with cardio-metabolic risk factors.Fund:European Union's Horizon 2020 research and innovation programme under grant agreement no. 633595DynaHEALTH.