Research in science education has shown that one's identities as science learner and teacher can mediate their pedagogical practices. Grounded in the perspective that language is a resource for identity (re)construction (Gee, 2000), the present study sought to understand how preservice science teachers' identities were manifested in their philosophies of science learning and teaching. Drawing on identity theory, we analyzed 76 essays (38 preservice teachers' science learning autobiographies and teaching philosophies) in terms of four dimensions of identity: nature, institution, discourse, and affinity. Our findings suggest that affinity identity plays an important role in shaping participants' science learning experiences and teaching philosophy. Ways to enhance preservice teachers' identities as science teachers and the relevance of adopting a discursive analytical approach to identity as a means of improving science teacher education programs are discussed.