Epidemiological and dietary intervention studies in humans and animals indicate that flavonoid consumption may be capable of promoting brain health. However, the knowledge regarding the brain bioavailability of flavonoids, and thus their potential for direct neuronal and glial actions, remains insufficient and inconsistent. If their direct actions on neurons are to be fully elucidated, knowledge regarding their transport across blood-brain barrier (BBB) and how this is regulated is crucial. Presently, there is sparse, but valuable information regarding the interaction of flavonoids and their metabolites with the BBB and their transfer across it. This review aims to highlight the existing knowledge with regards to these issues by two approaches: firstly by examining data emanating from in vitro studies, and secondly by appraisal of the existing in vivo data regarding flavonoid bioavailability to the brain.