This study examines collaboration between English for Speakers of Other Languages (ESOL) teachers and content-area elementary school teachers, and makes the case for conceptualising teacher collaboration as an opportunity for shared teacher learning. Using a sociocultural theoretical lens, this study examines how three pairs of elementary teachers and ESOL specialists used and constructed tools for collaboration, which mediated and made visible teachers' learning processes. Employing interpretive enquiry and cross-case analysis, we examined data from classroom observations, teacher co-planning sessions and interviews with teachers. Findings demonstrated that collaborating teachers used tools to articulate and reconceptualise teaching goals, co-construct knowledge and ultimately transform teaching practices to meet the needs of culturally and linguistically diverse students. This study has implications for teacher education and ongoing professional development, by shedding light on the potential affordances of collaborative tools for teacher learning. Findings suggest that teacher education could harness these opportunities for learning by incorporating collaboration between ESOL specialists and content-area teachers as an integral part of preparing more qualified teachers to work with culturally and linguistically diverse students.