Recent mathematics education research highlights the importance of developing rehumanising and critical mathematics pedagogies. The aim of this study is to develop a framework for affective content knowledge in mathematics and to apply that framework to instruction identified as supporting both mathematical learning (ML) and social emotional learning (SEL). Classroom observation and teacher interview data were collected in one primary and one secondary mathematics classroom in the United States and analysed qualitatively using case study methods. Two main findings are presented: 1) both teachers supported ML and SEL by modelling how to do and talk about mathematics with others; 2) both teachers leveraged affective content knowledge to provide instruction that supports ML and SEL. This study is significant because it describes how teachers in real classrooms are building affective content knowledge as part of a critical mathematics pedagogy that rehumanises the mathematics classroom.