Mindfulness-based stress reduction (MBSR) can help college students cope effectively with stress, reducing negative affect in the short term and resulting in higher (more adaptive) heart rate variability (HRV). However, HRV is a measure of cardiovascular fitness, as well as parasympathetic control of the stress response. MBSR is a multicomponent intervention and it is unclear to what extent movement, including gentle yoga, mindfulness training, or the synergy between the two, has an impact on emotional and physiological outcomes. The current study dismantled yoga and explicit mindfulness training in a brief stress reduction intervention in college students. Participants were randomly assigned to either mindfulness training and meditation alone (no movement); yoga alone (no explicit mindfulness training); combined yoga and mindfulness training and meditation; an active placebo control consisting of study breaks with party games, access to a therapy dog, and healthful snacks; or a no-treatment control. All active treatments resulted in decreases in anxiety and dysphoria over the 4 weeks of treatment relative to the no-treatment control, although by week 4, only the combined and yoga groups were significantly different from the control group on both measures. The no-treatment control group showed the lowest HRV at rest and during the challenge. The combined and yoga groups showed the highest HRV at rest, followed by moderate declines in HRV during the challenge, suggesting adaptive vagal withdrawal. The mindfulness training alone group was the only group to show no decrease in HRV during the challenge, suggesting that they were the least stressed by the challenge.