Subthreshold depression (StD) is common in older adults and is associated with poor self-rated health. However, the impact of StD on broader indicators of successful aging, such as positive psychological constructs, cognitive functioning, or quality of well-being, has not been assessed. The authors compared persons with scores above and below a predetermined threshold on the Center for Epidemiological Studies Scale for Depression (CES-D) with nondepressed (ND) persons on measures of multiple domains associated with successful aging.Cross-sectional survey-based psychological assessments.A total of 1,979 community-dwelling older women participating in the Women's Health Initiative study.ND was defined as a CES-D score below 8, StD as a score between 8 and 15, and CES-D Depression (CD) as a score of 16 or above. The study questionnaire consisted of multiple self-reported measures of positive psychological functioning (e.g., optimism and resilience), cognitive functioning and complaints, and quality of well-being. The authors also obtained a history of diagnosis, treatment, and hospitalization related to mental health problems.Overall 20.2% of women met CES-D criteria for StD and 7% for CD. Women with StD had worse self-rated successful aging, worse physical and emotional functioning, lower optimism, more negative attitudes toward aging, lower personal mastery and self-efficacy, and greater anxiety and hostility than ND women but scored better on all these measures than women with CD. Subjects with StD also had higher self-reported rates of previous diagnosis, treatment, and hospitalization for mental health problems than the ND group. Subjects with StD with depressed mood and/or anhedonia were largely similar to those without these symptoms.Mild-moderate levels of depressive symptoms that likely fall under a general category of StD were common and were associated with worse functioning on virtually every component of successful aging that the authors examined. StD represents a clinical entity that may affect the longitudinal course of successful aging for large numbers of persons and is a potential target for clinical intervention.