BACKGROUND: Our knowledge of the importance of flavonoid-rich foods in preventing unhealthy aging across its different domains is limited. OBJECTIVES: This study aimed to examine prospective associations between flavonoid-rich food and flavonoid intakes and indicators of unhealthy aging, namely frailty, impaired physical function, and poor mental health. METHODS: We followed up 62,743 females and 23,687 males, all aged ≥60 y, from the Nurses' Health Study (1990-2014) and Health Professionals Follow-up Study (2006-2018), respectively. Both time-updated and change in intakes of a flavodiet score (an aggregate of intakes of major flavonoid-rich foods and beverages) and individual flavonoid-rich foods and beverages and time-updated intakes of total flavonoids and flavonoid subclasses were calculated from food frequency questionnaires collected at baseline and every subsequent 4 y. Associations with incident frailty, impaired physical function, and poor mental health, assessed from self-reported questionnaire responses, were examined with multivariable-adjusted Cox proportional hazards models. RESULTS: In the Nurses' Health Study, participants with the highest flavodiet scores, compared with the lowest, had a 15% lower risk of frailty (HR CONCLUSIONS: High intakes of flavonoid-rich foods may support healthy aging. Further research is needed, including examining sex-specific associations, as incorporating flavonoid-rich foods in the diet may be a simple strategy to support healthy aging.