Objective: The quality of one's personal relationships has been reliably linked to important physical health outcomes, perhaps through the mechanism of physiological stress responses. Most studies of this mechanism have focused on whether more conscious interpersonal transactions influence cardiovascular reactivity. However, whether such relationships can be automatically activated in memory to influence physiological processes has not been determined. The primary aims of this study were to examine whether subliminal activation of relationships could influence health-relevant physiological processes and to examine this question in the context of a more general relationship model that incorporates both positive and negative dimensions. Method: We randomly assigned participants to be subliminally primed with existing relationships that varied in their underlying positivity and negativity (i.e., indifferent, supportive, aversive, ambivalent). They then performed acute psychological stressors while cardiovascular and self-report measures were assessed. Results: Priming negative relationships was associated with greater threat, lower feelings of control, and higher diastolic blood pressure reactivity during stress. Moreover, priming relationships high in positivity and negativity (ambivalent ties) was associated with the highest heart rate reactivity and greatest respiratory sinus arrhythmia decreases during stress. Exploratory analyses during the priming task itself suggested that the effects of negative primes on biological measures were prevalent across tasks, whereas the links to ambivalent ties was specific to the subsequent stressor task. Conclusions: These data highlight novel mechanisms by which social ties may impact cardiovascular health, and further suggest the importance of incorporating both positivity and negativity in the study of relationships and physical health.