This article illustrates how a classroom community characterized by "confianza"--a feeling of mutual understanding, respect, and emotional closeness--facilitated the English language learning of Spanish-speaking students in a content-based English as a second language class at a Puerto Rican public university. To understand the processes by which this language learning took place qualitative data were collected through classroom observations and focus groups. The authors examined the language choices students made in their interactions with professors, teaching assistants, and peers as they engaged in classroom conversations using both Spanish and English as learning tools. The central claim of the article is that "confianza" created the conditions through which learners were able to activate their zone of proximal development.