Critical multiculturalism and critical mathematics (or mathematics for social justice) have several common aspects. These include an acknowledgment of the importance of culture in education (in all its complexity and contestedness); a “critical” perspective on relations of power; and a commitment that education should prepare students to critique, challenge, and question the existing social order so that they can participate in the struggle for a more just world. In this chapter, I focus on the latter two and describe our critical mathematics theory and practice in an urban public high school in Chicago.