Interest in the role of emotion within mathematics education has increased in recent decades. Within a case-study framework, I explored how an Affective Instructional Design (AID) supported an early years teacher develop the capacity to change her instructional approaches, influenced her mathematic affect, and the affective experiences of her students. My conceptualisation for AID is based on an integrated framework approach drawing from emotion-learning theory, instructional design theory, and teaching and learning mathematics theory to integrate affect and cognition throughout the instructional process. Participants included 15 kindergarten children and their class teacher from a K-12 school in Tennessee, USA. Measures included teacher interviews, video recordings of 13 mathematics lessons, and field notes. Findings from this small study suggest instructional supports such as AID influence teacher capacity to bridge new learning and enacted practice; preliminary findings indicate AID contributed to a rise in positive teacher and learner affect, and improved teacher capacity to plan and implement quality mathematics learning environments.