This chapter describes how one teacher’s innovative attempts to promote powerful positive affect (PPA) in her Mathematics classroom gave rise to the development of concerns and tensions related to her practice. Tensions and concerns are identified and discussed using the theoretical tools of Activity Theory (AT) (Engestrom, 1987) and the Stages of Concern (SoC) (Hall & Hord, 2006). The findings suggest that using these tools together provides a helpful theoretical lens through which researchers can understand the challenges of change and teachers’ specific professional development needs. The identification and resolution of these tensions is of crucial importance for understanding and facilitating the efforts of sustainable pedagogical change. This chapter highlights the tensions and concerns of one participant as she attempted to promote PPA.