In this study, we explored whether the degree of temporal instability in relationship satisfaction might add to our understanding of the well-documented association between relationship quality and depression. We hypothesized that greater relationship satisfaction instability would be associated with higher depressive symptoms, controlling for mean satisfaction levels. We conducted 12 weekly assessments of relationship satisfaction and depressive symptoms in a sample of 131 cohabiting and married women, and used intraindividual standard deviations of scores over the 12 weeks as an index of instability. Results indicated that, as hypothesized, relationship satisfaction instability predicted variance in depressive symptoms beyond that predicted by mean satisfaction; women whose weekly relationship satisfaction fluctuated more widely tended to have higher depressive symptoms. In comparison, temporal instability in depressive symptoms did not predict variance in relationship satisfaction beyond that predicted by mean depressive symptoms. Prospective analyses tentatively suggested that satisfaction instability may precede rather than follow elevated depressive symptoms. Results suggest the utility of assessing relationship satisfaction instability in future studies exploring links between marital quality and depression.