This study examined elementary preservice teachers’ knowledge and application of science vocabulary during peer teaching. The purpose of this study was to: (1) examine preservice teachers’ knowledge of elementary science vocabulary at the beginning and end of a science methods course, and (2) document preservice teachers’ use of elementary science vocabulary commonly used in elementary science instruction during initial science teaching experiences. The data reveal that preservice teachers’ initial knowledge of elementary science vocabulary was lacking , despite the successful completion of high school and college science coursework. The findings indicate that the course positively impacted the preservice teachers’ knowledge of select elementary science vocabulary.