Drawing from a relational developmental systems (RDS) perspective (Lerner, Agans, DeSouza, & Gasca, 2013) and data from 1,427 continuously partnered young adult and midlife mixed-sex couples over the first 5 years of the German Panel Analysis of Intimate Relationships and Family Dynamics (pairfam), this study examined the developmental course of supportive dyadic coping, or the frequency with which one provides practical and emotional support when his or her partner encounters stress. Latent change score (LCS) modeling results revealed that supportive dyadic coping gradually declined for both male and female partners, but there was significant diversity underlying these trajectories. Higher levels of supportive dyadic coping were associated with a more gradual decline in support provided by a partner. Among young adults, a more rapid decline in male partner supportive dyadic coping predicted a slower rate of decline in support from female partners. Finally, we considered possible bidirectional relations between contextual stressors and supportive dyadic coping trajectories. Providing higher levels of support predicted a more gradual decline in self-rated health for male partners. Having more children and experiencing economic pressure predicted steeper declines in supportive dyadic coping over time for both male and female partners.