Postmenopausal women are at increased risk for progression of arteriosclerosis and hypertension. Recent cross-sectional evidence suggests that high normal circulating prolactin levels may accelerate vascular ageing in menopause. Postmenopausal women (n = 201) were consecutively recruited from a Menopause Clinic and re-evaluated in at least one follow-up visit within the next 3 years. Baseline circulating prolactin levels were measured while both baseline and follow-up vascular and biochemical measurements were performed. Endothelial function was assessed by flow-mediated dilation (FMD), aortic stiffness by pulse-wave velocity (PWV) and arterial wave reflections by applanation tonometry. Baseline prolactin significantly correlated with lower FMD at follow-up (P = 0.005). After multivariable adjustment for age, follow-up time, blood pressure (BP), body mass index, smoking and medication, this correlation remained significant (P = 0.003). In addition, baseline circulating prolactin levels were independently associated with changes in mean BP (β = 0.131, P = 0.021), peripheral diastolic BP (β = 0.169, P = 0.004) and new-onset hypertension (OR = 1.235, P = 0.001). Owing to significant interaction between baseline prolactin and age for changes in PWV over time (P = 0.036), a subgroup analysis based on median age was performed. This analysis revealed that in women younger than 55 years, prolactin was an independent predictor of changes in PWV over time (P = 0.008). In conclusion, high normal circulating prolactin levels predict changes in haemodynamic indices and worsening endothelial function in healthy postmenopausal women. Particularly in young postmenopausal women, prolactin predicts accelerated arterial stiffening.