Attitudes are at the heart of the Theory of Reasoned Action (TRA), but problems in defining and measuring attitudes have contributed to typically low ability to predict behaviour. This article investigates the impact of potential disjuncture between evaluations that an individual externally verbalises (explicit attitudes), and evaluations that are internally held and may exist outside of conscious awareness (implicit attitudes), on the predictive ability of TRA. We study consumers’ attitudes towards eating healthy food and subsequent behaviour in a context of socially consensual behaviour. An Implicit Association Test (IAT) is used to measure implicit attitudes, and these scores are contrasted with self-reported explicit attitude scores. Ninety one participants took part in the study. We found, surprisingly, that implicit attitude has no significant effect on behavioural intention. However, a disjuncture between an individual’s implicit and explicit attitudes, reflecting internal psychological conflict, affected behaviour.