Marital discord fuels depression, according to decades of research. Most prior studies in this area have focused on macro-longitudinal change in depression over the course of years, and on global ratings of marital satisfaction. Less work has examined fluctuations in depressed mood and marital discord in daily life, and none has investigated associations of short-term patterns with longer-term depressed mood and marital outcomes. Using data from participants in the Midlife in the U.S. (MIDUS) project, the current study examined daily associations between marital discord and depressed mood, as well as their links to concurrent and prospective patterns of past-month depressed mood and marital risk. Results showed that, on average, depressed mood rose on days when individuals had an argument or tension with their spouse (i.e., marital discord). More frequent daily marital discord was also associated with greater past-month depressed mood and marital risk, above and beyond prior levels. Those with larger depressive mood responses to discord in daily life (i.e., greater reactivity) exhibited higher concurrent past-month depressed mood and greater 10-year increases in depressed mood. As the first study to link daily marital patterns to concurrent and prospective changes in depressed mood and marital outcomes, this investigation uncovered two novel processes-daily marital discord and depressive reactivity-as important for understanding long-term patterns of marital risk and depression.