Co-design approaches have roots in participatory research design methodologies, amplifying participants' experiences, cultures, and beliefs by co-designing or co-creating an artifact or activity for and with other people. Little research has incorporated Spanish-speaking Latine families in co-designing early math tools and resources. Therefore, this study explored how six Latina mothers engaged in co-creating a math activity for their children. The results revealed that Latina mothers used cultural repertoires to navigate the co-design sessions and construct mathematical knowledge. Additionally, this study found that co-design methods centered Latina mothers as designers and users of their own math learning experience, positioning them as experts in their own learning and allowing for the co-creation of a meaningful math learning experience. These results provide insights into how co-design methods herald a different, more engaging way to involve Latine families in the design of math learning experiences and tools to standard family engagement interventions.