Research-based science curriculum has become a common means of supporting best practices in science teaching. In response to his middle school's transition from one such commercially available science curriculum to another, a seventh-grade science teacher elected to make certain changes to the newly adopted curriculum in its first year of use. These curricular adaptations took place despite a district directive to pilot the curriculum without making any such changes. The purpose of this phenomenological study was to understand this teacher's lived experience adapting the curriculum. The values that guided this teacher's curricular decisions situated his life world construction of a science teaching identity around an unremitting pedagogy that maintained his use of best practices. His identity construct further exposed certain self-understandings he held as a science teacher and understandings of his students as science learners. It was the intersection of these pedagogical values with those understandings of his students and himself that supported these curricular changes, providing the backdrop for his identity construct. Therefore, the construction of a science teaching identity, which relies on this intersection, offers deepened insight into teachers' implementation of reform-based curriculum.