--- - |2 Social support in marriage may be associated with reduced risk for mental illness. Past studies are limited by short follow up and a focus on depression. A two‐wave nationally representative survey in the United States (n = 2,503) is used to examine whether social support in marriage is associated with the onset of each of four clusters of disorders—internalizing, externalizing, phobic, and bipolar—10 years later. Results indicate that higher levels of perceived marital support were protective against internalizing, fear, and bipolar disorders, and against incident externalizing disorders for women. Protective effects of social support in marriage against mental illness are long‐lasting, and sometimes differ by gender. Findings suggest the importance of mental health assessment in clinical practice. - Journal of Marital and Family Therapy, EarlyView.