This study examined the role of science identity in a two-year upper-division research training program that prepares diverse undergraduate students for a research career. Using the annual year-end student evaluation data, we examined whether science identity is a predictor or an outcome of learning that enhances career preparation in biomedical research. Results showed that science identity is a predictor of learning in our trainees. In general, students with stronger science identity at the end of Year 2 reported having acquired more research skills and experiences through the program. This finding demonstrates that science identity makes learning research skills meaningful and purposeful. Preliminary analyses also showed that the levels of science identity did not differ between Years 1 and 2. In fact, science identity approached the maximum possible scores in both years. These findings imply that the training program could have succeeded in bolstering participants' science identity early by the end of the first year. Our findings do not rule out the possibility that science identity is both a predictor and an outcome of learning, depending on the specific contexts of learning as well as learners' specific developmental phases. Further studies are needed to systematically test these and other possibilities.