The Collaborative for Academic, Social, and Emotional Learning (CASEL) identifies five core, interrelated social and emotional learning (SEL) competencies that children need to be successful in school, at home, and in their community: (1) self-awareness; (2) self-management; (3) responsible decision-making; (4) relationship skills; and (5) social awareness. SEL is critical in early childhood, throughout elementary school, and beyond. A Number Talk is a short activity--usually 5 to 15 minutes long--during which a teacher facilitates a discussion with a whole class or a small group of children about a carefully designed problem or sequence of problems. During Number Talks, children solve problems mentally and then discuss solutions and strategies; the teacher facilitates the discussion with open-ended questions that prompt children to communicate their own ideas about problems and consider the ideas of others. This article illustrates how as a pedagogical tool, Number Talks present a rich opportunity for teachers to foster children's SEL. The article also offers suggestions for supporting SEL competencies during Number Talks. Although Number Talks are a specialized mathematics classroom discussion (and therefore offer a concrete example of ways to specifically incorporate SEL support), the ideas for supporting children's SEL presented here apply to mathematics classroom discussion generally.