Can stress ever be good for romantic relationships? Although it is well-established that stress can harm relationships (Karney & Bradbury, 1995; Randall & Bodenmann, 2009), stress may also bring people closer together (Taylor, 2011b). Specifically, recent research and theory suggest that when people experience acute and chronic stress that originates outside of the couple (i.e., external stress) and is moderate in intensity, they may show affiliative responses toward their partner (Clavel et al., 2017; Donato et al., 2018). Moreover, stressed women may be more likely to show affiliative responses toward their partner than stressed men (Taylor et al., 2000. Importantly, how much a person displays affiliative responses may not only depend on their own stress but also their partner’s stress. However, there is currently little research examining both partners’ stress and affiliative responses. Thus, the current dissertation examines affiliative responses in couples experiencing acute and chronic external stress. This research aims to understand (1) when external stress may be associated with more affiliative responses and (2) who may show more affiliative responses to external stress. In three studies, I examined stress and affiliation during the COVID-19 pandemic, during a laboratory stressor, and during a dyadic caregiving interaction with an infant simulator. I found that moderate acute stress may be associated with greater affiliation in women and lower affiliation in men, shared acute and chronic stressors may be associated with greater affiliation, and people may respond to their partner’s stress by affiliating with their simulated infant. This work contributes important new information about how external stress may affect men and women in romantic relationships.