This study examines the relationship between language attitudes and language use from a social cognition perspective in the context of Catalonia, a culturally and linguistically diverse Spanish Autonomous Community that has been implementing social and educational measures to promote the use of its own language, Catalan. We examined how implicit and explicit measures of attitudes towards Catalan and Spanish predict self-reported language use and spontaneous language choice. Participants (N = 98) completed an Implicit Association Test (IAT), self-reports of language attitudes and use, and a spontaneous language choice. Although both implicit and explicit measures correlated with the behavioural measures, the results showed that the IAT had predictive and incremental validity. Moreover, a partial dissociation pattern of prediction was identified, underscoring the importance of including implicit measures of language attitudes, as they predict variance in behaviour above and beyond what is predicted by explicit measures.