In the United States, there is a need for pedagogical tools that help teachers develop essential pedagogical content knowledge and practices to meet the mathematical education needs of a growing culturally and linguistically diverse student population. In this article, we introduce an innovative lesson analysis tool that focuses on integrating mathematical thinking, language, culture, and social justice. We argue that these are essential components to culturally responsive mathematics teaching. Using data collected from a 3-year professional development initiative focused on culturally responsive mathematics teaching including teacher discussions, lesson artefacts, and interviews, the study yields two main results about the tool and its impact on teacher thinking: (1) the tool enabled teachers to systematically analyse and critique mathematics lessons with multiple dimensions including mathematical thinking, language, culture, and social justice; (2) the tool fostered purposeful pedagogical dialogue to improve a mathematics lesson along specific culturally responsive dimensions. The findings illustrate the potential of this tool to engage teachers in strategic lesson planning and purposeful discussions to make mathematics lessons culturally responsive and improve the quality of mathematics teaching in the classroom.