With the increasing advocacy for Computational Thinking (CT) integration in K-12 education, it is important to consider how teacher education programs could better prepare teacher candidates (TCs). At the Faculty of Education at Western University, CT has been included in the curriculum as part of the teacher education program through the course "Computational Thinking in Mathematics and Science Education," oriented to Intermediate/Senior (Grades 7 to 12) preservice teachers. In this paper, we describe the case study of the 2017 cohort of the CT course (Fall 2017). We aimed to answer the question: What key understandings about CT did teacher candidates develop through their participation in the course? We found that TCs in our course developed a better understanding of: (1) CT connections to the real world, as well as lesson ideas and pedagogical examples to integrate CT in the context of mathematics and science; (2) the different affordances of CT integration; (3) the use of several technologies to implement CT integration; and (4) what CT is, as well as the set of skills that contribute to its development.