External stressors can detriment relationship quality, though little is known about what can mitigate these effects. In the current study, we examine whether COVID-related stressors are associated with lower relationship quality and test whether perceived partner responsiveness—the extent to which people believe their partner understands, validates, and cares for them—buffers these effects. In the current study (N = 3,593 participants from 57 countries), when people in relationships reported more COVID-related stressors they also reported poorer relationship quality at the onset of the pandemic and over the subsequent three months. However, in most cases, these associations were attenuated or buffered by people’s perception of their partner’s responsiveness, such that people who perceived their partners to be low in responsiveness reported poorer relationship quality when they experienced COVID-related stressors, but these associations were reduced among people who perceived their partners to be highly responsive.