Meta-analyses suggest a small association between cardiovascular responses to acute stressors and cardiovascular disease, but a recent review suggests that this effect may be underestimated due to insufficient consideration of individual differences in habituation to repeated stressors. Objective: The present article reports new analyses of a published randomized controlled trial comparing the effects of mindfulness-based stress reduction (MBSR), cognitive behavioral therapy (CBT), and a passive control condition on blood pressure habituation-a secondary outcome. Psychological mediators of intervention effects were examined. Method: Participants (138 healthy adults reporting moderate/high stress) were randomly assigned to 6-week MBSR, CBT, or a waitlist control. Analyses were conducted on 86 participants who subsequently completed stressful speech and mental arithmetic tasks during two posttreatment visits scheduled 48 hr apart. Blood pressure was measured Ϫ15, ϩ0, ϩ5, ϩ10, ϩ25, ϩ35, and ϩ60 min poststressor onset. Results: There were no between-condition differences in blood pressure habituation (all ps Ͼ .05). However, both MBSR and CBT led to increased perceived control over thoughts, F(2, 72) ϭ 5.20, p ϭ .008, and individuals who displayed a greater change in perceived control over thoughts also displayed greater habituation to the speech portion of the stressor, F(6, 799) ϭ 2.32, p ϭ .020. Results implied an indirect effect of stress reduction interventions on blood pressure habituation via change in perceived control over thoughts (b ϭ Ϫ3.93, SE ϭ 1.98, 95% CI: [Ϫ8.392, Ϫ0.701]). Conclusion: Stress reduction interventions that increase perceived control over thoughts may benefit cardiovascular health by promoting blood pressure habituation.