This research examines the influence of bilingualism on third language learning in a bilingual community, the Basque Country. The English-language achievement of students instructed through the majority (Spanish) and the minority (Basque) languages in the Basque Country was measured. In addition, other cognitive, sociostructural, social psychological, and educational variables were also included in the study. Several sets of regression analyses were carried out to analyze the role of bilingual education. The results indicated that bilingualism and several other variables (intelligence, motivation, age, and exposure) were good predictors of English-language achievement. This research suggests, then, that immersion in the minority language for Spanish-speaking students and school reinforcement of the native language for Basque-speaking students have positive linguistic outcomes.