["Psychophysiology, Volume 63, Issue 5, May 2026. ", "\nABSTRACT\nThis study examined whether multiple group membership (MGM) predicted future cardiovascular reactivity (CVR) in women and whether this relationship was moderated by the number of social group memberships they perceived to be the basis for their discrimination. Using a longitudinal design, data were drawn from Waves 2 and 3 of the Midlife in the United States (MIDUS) study. The sample included 179 women for diastolic and systolic blood pressure (DBP, SBP) reactivity and 200 women for heart rate (HR) reactivity (ages 47–94, M = 63.66, SD = 8.90). Greater MGM at Time 1 was associated with lower HR responses to stress at Time 2, indicating reduced cardiovascular responding during the stress tasks. Moderation analyses revealed that among women who attributed discrimination to one group, higher MGM predicted higher HR reactivity suggesting a more engaged stress response. In contrast, among women who did not attribute discrimination to any group, higher MGM was significantly associated with lower HR reactivity. No significant effects were found for SBP and DBP reactivity. Together, these findings suggest that MGM does not uniformly confer stress‐buffering benefits and may, in some contexts, reflect cumulative social burden rather than protection. The results highlight the importance of considering the social meaning and context of group memberships, particularly experiences of discrimination, when evaluating their implications for women's stress‐related health.\n"]