There is growing evidence for a protective effect of breastfeeding against overweight and diabetes. It is less clear though, whether breastfed infants also have a more favorable cardiometabolic profile in childhood.We investigated whether children who were breastfed in infancy had more favorable cardiometabolic markers at 12 years of age than children who were never breastfed and received formula milk instead, and whether associations depended on the duration of breastfeeding.In 1509 participants of the population-based PIAMA birth cohort study, cardiometabolic markers were measured at 12 years of age. Duration of breastfeeding in weeks was assessed through parental questionnaires at 3 months and 1 year of age. Multivariable linear regression analysis was used to investigate associations of breastfeeding (any vs. never breastfeeding and duration of breastfeeding in categories <3 months, 3 to <6 months, and ≥6 months breastfeeding vs. never breastfeeding) with systolic and diastolic blood pressure (SBP and DBP, in Z-scores adjusted for age, sex, and height), total-to-high-density lipoprotein cholesterol (TC/HDLC), glycated hemoglobin (HbA1c, in mmol/mol), body mass index (BMI, in Z-scores adjusted for age and sex) and waist circumference (WC, in cm). Multivariable logistic regression was used to investigate the association of breastfeeding with odds of being overweight.1288 of 1509 children (85.3%) received any breastmilk in infancy. Breastfed children had a lower SBP Z-score (-0.21 SD (≈ -2.29 mmHg), 95% CI -0.37, -0.06), a lower DBP Z-score (-0.10 SD (≈ -1.19 mmHg), 95% CI -0.20, -0.00), a smaller WC (-1.12 cm, 95% CI -2.20; -0.04), and lower odds of being overweight (OR 0.61, 95% CI 0.38, 0.97) than never breastfed children. These associations were not different between children with shorter and longer duration of breastfeeding. No statistically significant differences in TC/HDLC, HbA1c, and BMI were observed between breastfed and never breastfed children.We observed that breastfeeding was associated with a lower blood pressure, a smaller waist circumference and a lower risk of overweight in 12-year old children. These associations were independent of the duration of breastfeeding. No associations were observed between breastfeeding and other cardiometabolic markers.