Periods of bond formation are accompanied by physiological and emotional changes, yet, little is known about the effects of falling in love on the individual's physiological response to emotions. We examined autonomic reactivity to the presentation of negative and positive films in 112 young adults, including 57 singles and 55 new lovers who began a romantic relationship 2.5 months prior to the experiment Autonomic reactivity was measured by Respiratory Sinus Arrhythmia (RSA) to two baseline emotionally neutral films, two negative films, and two positive films. Results demonstrated that RSA in singles decreased during the presentation of negative emotions, indicating physiological stress response. However, no such decrease was found among new lovers, pointing to more optimal vagal regulation during the period of falling in love. Autonomic reactivity, indexed by RSA decrease from the positive to the negative films, was greater among singles as compared to lovers, suggesting that love buffers against autonomic stress and facilitates emotion regulation. Findings suggest that vagal regulation may be one mechanism through which love and attachment reduce stress and promote well-being and health.