This article examines a culturally sustaining approach to learning about and enacting multimodal literacy instruction that was developed during a field-based reading methods course for elementary preservice teachers. Despite a large body of work exploring preservice teachers' learning about multimodal literacies, few studies have explored their experiences incorporating multimodal literacies from an explicitly culturally sustaining lens, nor examined learning about multimodal instruction in field-based settings. In this qualitative case study, we explore the ways in which one preservice teacher's experiences in a field-based reading methods course impacted her conception of multimodal literacies and her understanding of the cultural and semiotic resources of diverse students. The findings detail the culturally sustaining, multimodal literacy instruction that emerged from a mentoring dyad of the focal preservice teacher and a second-grade multilingual student, the preservice teacher's developing conceptions of multimodal literacy, and the conditions of learning that facilitated her teaching and learning.