Using a randomized, double-blinded, placebo-controlled, parallel group design, this investigation determined if the combination of 2-weeks flavonoid supplementation (329 mg/day, quercetin, anthocyanins, flavan-3-ols mixture) and a 45-minute walking bout (62.2±0.9% VO2max) enhanced the translocation of gut-derived phenolics into circulation in a group of walkers (N = 77). The walkers (flavonoid, placebo groups) were randomized to either sit or walk briskly on treadmills for 45 minutes (thus four groups: placebo-sit, placebo-walk, flavonoid-sit, flavonoid-walk). A comparator group of runners (N = 19) ingested a double flavonoid dose for 2 weeks (658 mg/day) and ran for 2.5 h (69.2±1.2% VO2max). Four blood samples were collected (pre- and post-supplementation, immediately-post- and 24-h post-exercise/rest). Of the 76 metabolites detected in this targeted analysis, 15 increased after the 2.5-h run, and when grouped were also elevated post-exercise (versus placebo-sit) for the placebo- and flavonoid-walking groups (P < 0.05). A secondary analysis showed that pre-study plasma concentrations of gut-derived phenolics in the runners were 40% higher compared to walkers (P = 0.031). These data indicate that acute exercise bouts (brisk walking, intensive running) are linked to an increased translocation of gut-derived phenolics into circulation, an effect that is amplified when combined with a 2-week period of increased flavonoid intake or chronic training as a runner.