Noticing students' mathematical strengths is a complex skill that prospective teachers need to learn. To this end, a teacher education course was designed to engage prospective mathematics teachers in critically reflecting on their individual and collectively shared framings of students' mathematical understanding, thereby effecting a change in their orientations in noticing students' mathematical thinking. This study identifies teachers' framings of students' mathematical understanding and examines the nature and development of teachers' noticing of students' mathematical strengths. Specifically, the study identifies a typology of deficit-oriented and strength-oriented framings in noticing students' mathematical thinking and demonstrates how shifts in framings promote changes in prospective teachers' attention, interpretation, and response to students' mathematical thinking.