Affectionate communication comprises the verbal and nonverbal behaviors people use to express messages of love, appreciation, fondness, and commitment to others in close relationships. Like all interpersonal behaviors, affectionate communication has biological and physiological antecedents, consequences, and correlates, many of which have implications for physical health and wellness. Investigating these factors within a biological framework allows for the adjudication of influences beyond those attributable to the environment. In particular, there are observable genetic and neurological differences between individuals with a highly affectionate disposition and those less prone to communicating affection, suggesting that variance in the tendency to engage in affectionate behavior is not entirely the result of environmental influences such as enculturation, parenting, and media exposure. In addition, the expression of affection is associated with markers of immune system competence and appears to help the body to relax and remain calm. The biological effects of affectionate communication are perhaps most pronounced in situations involving either acute or chronic stress. Specifically, highly affectionate individuals are less likely than others to overreact physiologically to stress-inducing events. Whatever stress reaction they do mount is better regulated than among their less affectionate counterparts. Moreover, highly affectionate individuals—or simply those who receive expressions of affection prior to or immediately following a stressful situation—exhibit faster physiological recovery from their elevated stress. Perhaps unsurprisingly, therefore, being deprived of adequate affectionate communication is predictive of multiple physical and psychological detriments, including elevated stress and exacerbated depression, social and relational problems, insecure attachment, susceptibility to diagnosed anxiety and mood disorders, susceptibility to diagnosed secondary immune disorders, chronic pain, and sleep disturbances.