Abstract Background Breastfeeding is important for both mother and child in reducing risk of future cardiovascular disease. Therefore, it may be an effective method to improve cardio-metabolic health, particularly those who are exposed to pregnancy complications which increase later CVD risk for both mother and child. The aim of this study is to assess differences in cardiometabolic health at three years postpartum in mothers who breastfed for at least six months and their children compared to those who did not. Methods Women and children from the Screening Tests to Predict Poor Outcomes of Pregnancy (STOP) study (2015–2017) were invited to attend a health check-up at three years postpartum. Women’s breastfeeding status at least six months postpartum was ascertained through their child health record. Anthropometric and hemodynamic measurements were taken from women and their children. A fasting blood sample was taken from women to measure blood glucose and lipids. Results A total of 160 woman-child dyads were assessed in this study. Women who breastfed for at least six months had significantly lower maternal BMI, systolic blood pressure, diastolic blood pressure, mean arterial pressure, central systolic blood pressure, and central diastolic blood pressure than those who did not and this did not change after adjusting for BMI and socioeconomic index in early pregnancy, prenatal smoking and maternal age in early pregnancy. Subgroup analysis on women who had one or more pregnancy complications during the index pregnancy (i.e. preeclampsia, gestational hypertension, delivery of a small for gestational age infant, delivery of a preterm infant, and/or gestational diabetes mellitus) demonstrated that women who breastfed for at least six months had significantly lower maternal systolic and diastolic blood pressures, serum insulin and triglycerides, and higher HDL cholesterol. There were no differences in child anthropometric or hemodynamic variables at three years of age between those children who had been breastfed for at least six months and those who had not. Conclusion Breastfeeding for at least six months may reduce some maternal; cardiovascular risk factors in women at three years postpartum, in particular, in those who have experienced a complication of pregnancy. Trial registration ACTRN12614000985684 (12/09/2014).