This study explores the development of professional identity as a teacher of nature of science (NOS). Our research question was "How can a teacher develop a professional identity as an elementary teacher of NOS?" Through a researcher log, videotaped lessons, and collection of student work, we were able to track efforts in teaching NOS as part of regular classroom practice. A team of four researchers interpreted the data through the Beijaard et al. professional identity framework and found that it was not as simple and straightforward to teach NOS as we predicted. Development of professional identity as a teacher of NOS was influenced by contextual factors such as students, administration, and time, as well as personal struggles that were fraught with emotion. Development took place through an interpretation and reinterpretation of self through external factors and others' perceptions, as well as the influence of sub-identities.