Objective: Menopause may augment age-dependent increases in arterial stiffness, with black women having greater progression in midlife compared with white women. We sought to determine whether and when women experience changes in arterial stiffness relative to the final menstrual period (FMP) and whether these changes differ between black and white midlife women. Approach and Results: We evaluated 339 participants from the SWAN (Study of Women’s Health Across the Nation) Heart Ancillary study (Study of Women’s Health Across the Nation). Women had ≤2 carotid-femoral pulse-wave velocity (cfPWV) exams over a mean±SD of 2.3±0.5 years of follow-up. Annual percentage changes in cfPWV were estimated in 3 time segments relative to FMP and compared using piecewise linear mixed-effects models. At baseline, women were 51.1±2.8 years of age and 36% black. Annual percentage change (95% CI) in cfPWV varied by time segments: 0.9% (−0.6% to 2.3%) for >1 year before FMP, 7.5% (4.1% to 11.1%) within 1 year of FMP, and −1.0% (−2.8% to 0.8%) for >1 year after FMP. Annual percentage change in cfPWV within 1 year of FMP was significantly greater than the other 2 time segments; P <0.05 for both comparisons. Adjusting for concurrent cardiovascular disease risk factors explained part of the change estimates but did not eliminate the difference. Black women had greater increase in cfPWV compared with white women in the first segment; P for interaction, 0.04. Conclusions: The interval within 1 year of FMP is a critical period for women when vascular functional alterations occur. These findings underscore the importance of more intensive lifestyle modifications in women transitioning through menopause.