According to the neurocognitive framework for regulation expectation, adaptively regulating emotions in anticipation of a stressful event should help individuals deal with the stressor itself. The goal of this study was twofold: first, the authors compared the influence of adaptive versus maladaptive anticipatory emotion regulation (ER) on the autonomic system during anticipation of, confrontation with, and recovery from a stressor; second, they explored whether trait rumination moderated this relationship. The authors collected data from 56 healthy female undergraduates during a public speaking task. The task involved 4 phases: baseline, anticipatory ER, stressor, and recovery. Participants were assigned to 1 of 2 anticipatory ER instructions (reappraisal or catastrophizing). Heart rate variability (HRV) indexed autonomic regulation. Results confirmed that HRV was higher in the reappraisal than in the catastrophizing group (over all time points, except for baseline). Trait rumination levels moderated the effect of anticipatory ER strategy on HRV during the stressor phase. Specifically, whereas for low ruminators reappraisal (versus catastrophizing) in the anticipation phase led to higher HRV when confronted to the stressor, high ruminators demonstrated lower HRV in that same condition. To conclude, over all participants, using reappraisal during the anticipation phase allowed participants to better cope with stress. However, only low, but not high ruminators could profit from the beneficial effect of anticipatory reappraisal on autonomic regulation. Even though further research is needed, this study suggests that, in female undergraduates, the tendency to ruminate is associated with abnormal anticipatory ER that might hinder an adaptive response to a stressor. (PsycINFO Database Record (c) 2019 APA, all rights reserved).