Evidence has emerged supporting the antidepressant-like effect of foods with high flavonoid content, like fruits, vegetables, and various beverages. Literature searches from PubMed, Scopus, and Web of Science found 36 clinical trials to include in the meta-analysis and 10 observational cohort studies for the systematic review. Most studies were randomized, blinded, and included male and female participants aged > 40. Most of the trials tested the clinical effects of flavonoids consumed as tablets, pills, powders, or liquids. The meta-analysis revealed a statistically significant reduction in depressive symptoms in participants (n = 2788) following consumption of dietary flavonoids, specifically from the flavonoid subclasses isoflavones, flavonols, and flavan3-ols. Of the 10 observational studies included in the systematic review, 5 suggested a diet higher in flavonoids could improve symptoms of depression. Authors performed a quality assessment of all studies and trials before they were included in the current study and evaluated publication bias using a funnel plot and Egger’s test. Authors concluded that while there is evidence to support flavonoids as beneficial for depressive symptoms, more research is required to evaluate them as a dietary prevention measure specifically against symptoms of Major Depressive Disorder.