This study examined bilingual preservice teachers' self-efficacy in the context of lesson differentiation for multilingual learners in Spanish. Thirty-six bilingual preservice teachers across three California State University programs participated in a quantitative methods study of lesson plan analysis. Findings showed that preservice teachers were not sufficiently skilled at differentiating instruction for learners with distinct linguistic needs and assets. Results indicated that, although preservice teachers had high levels of English learner (EL) teaching self-efficacy towards multilingual learners, there was low correlation with their ability to provide lesson differentiation. The study concluded that differentiation is a complex process that requires extensive knowledge of content standards, understanding students' linguistic assets, and enacting purposeful high-leverage strategies with supports and scaffolds to meet multilingual learners' needs.