Background The global prevalence of obesity in women keeps increasing. The preconception period may be a window of opportunity to improve lifestyle, reduce obesity and improve cardiometabolic health. This study assessed the effect of a preconception lifestyle intervention on long-term cardiometabolic health in two randomized controlled trials (RCTs). Methods Participants of the LIFEstyle and RADIEL preconception lifestyle intervention studies with a baseline body mass index (BMI) ≥29 kg/m 2 were eligible for this follow-up study. Both studies randomized between a lifestyle intervention targeting physical activity, diet and behaviour modification or usual care. We assessed cardiometabolic health 6 years after randomization. Results In the LIFEstyle study (n = 111) and RADIEL study (n = 39), no statistically significant differences between the intervention and control groups were found for body composition, blood pressure, arterial stiffness, fasting glucose, homeostasis model assessment of insulin resistance, HbA1c, lipids and high sensitive C-reactive protein levels 6 years after randomization. Participants of the LIFEstyle study who successfully lost ≥5% bodyweight or reached a BMI <29 kg/m 2 during the intervention (n = 22, [44%]) had lower weight (-8.1 kg; 99% CI [-16.6 to -0.9]), BMI (-3.3 kg/m 2; [-6.5 to -0.8]), waist circumference (-8.2 cm; [-15.3 to -1.3]), fasting glucose (-0.5 mmol/L; [-1.1 to -0.0]), HbA1c (-4.1 mmol/mol; [-9.1 to -0.8]), and higher HDL-C (0.3 mmol/L; [0.1-0.5]) compared with controls. Conclusion We found no evidence of improved cardiometabolic health 6 years after a preconception lifestyle intervention among overweight and obese women in two RCTs. Women who successfully lost weight during the intervention had better cardiometabolic health 6 years later, emphasizing the potential of successful preconception lifestyle improvement.