As computational thinking (CT) is increasing in focus in K-12 education, it is important to consider how teacher education programs may better prepare teacher candidates (TCs). Previous studies have found that TCs do not always have a firm understanding of what CT involves, and they might not have clear ideas about how to develop CT in their future classrooms. In this context, the authors developed a course for elementary school TCs focusing on CT in mathematics education. The course integrated CT in the context of mathematics activities to help TCs develop both a conceptual understanding of mathematics and mathematics teaching with CT. The paper presents a case study analysis of TCs' online discussions and reflection assignments of the course, as well as themes in their learning about and attitudes toward CT in mathematics teaching and learning.