A critical component to disciplinary engagement in science is that of epistemic affect--learning how to "feel" as scientists do when engaged in their work. The emotional responses, feelings, and dispositions that emerge as one participates in the construction of knowledge are part and parcel to the experiences of scientists and, we argue, should be integral to the experiences of science learners--and their teachers--as well. As such, this study takes the position that teachers must have opportunities to encounter, understand, and appreciate the epistemic affect in science to support students in navigating their affect in the science classroom. Through analysis of field observations and semistructured interviews conducted during a 6-week Research Experience for Teachers program, this study examines how four elementary teachers experience an epistemic affect over the course of their engagement in scientific research. The findings of the study highlight that engaging in science research afforded teachers rich opportunities to experience epistemic affect, ranging from frustration, perseverance, and ultimately pride in their work. We argue such firsthand affective experiences within professional development programs featuring participation in science research hold important implications for teachers' instructional practice and orientations to their students as thinkers, doers, and learners of science.