Current renewed interest in the epistemological, socio-cultural, and educational aspects of indigenous knowledge systems (IKSs) has also had some impact on research and practice in the area of mathematics education. Located in the intersection of culture, mathematics, and classroom learning, this position article proposes that the socio-cultural activities of a cultural group can offer potentially rich contexts for developing mathematical ideas. Ways of exploiting that richness for classroom instructional purposes within the relevant cultural setting are then explored. A framework for mathematizing such ethno-activity based contexts that could guide mathematics teachers wishing to use this resource is presented. The framework has three phases, namely, conceptual analysis of a relevant syllabus topic/concept, horizontal mathematization of an appropriate cultural activity, and vertical mathematization based on the second phase. The processes and expected outcomes in each phase are discussed in the article.