Background: Flow is a peak experiential state, during which athletes report focused concentration, effortless performance and enhanced enjoyment. Flow, or ‘the zone’, has received particular interest within sporting circles because flow experiences appear to be associated with peak athletic performances. Yet, the nature of the flow-performance relationship is not straightforward and is yet to be critically reviewed. Objectives: This systematic review and meta-analysis sought to examine the empirical evidence for a flow-performance relationship, examine potential mechanisms, and assess the quality of current evidence. Methods: A PRISMA guided systematic review was conducted in May 2020. Peer-reviewed articles, published in English language journals, which examined the relationship between flow and performance were searched for, using five online databases. The results of the studies were collated into a narrative synthesis as well as a meta-analysis. Results: Twenty articles met the inclusion criteria, featuring 22 studies that were appropriate for meta-analysis. The pooled effect size (r = 0.31, 95% CI [0.24; 0.38]) indicated that across a range of sporting and gaming tasks there was a consistent medium-sized relationship between flow experience and task performance. A number of mechanisms were proposed to explain this relationship, but none were supported by convincing empirical evidence. Conclusions: Performance enhancing effects appear highly likely given the functional mental state that arises during flow. Yet, current evidence is unable to determine the exact nature of the flow-performance relationship, or the mechanisms which mediate this effect. A number of conceptual and methodological challenges