Science vocabulary knowledge plays a role in understanding science concepts, and science knowledge is measured in part by correct use of science vocabulary (Lee et al. in "J Res Sci Teach" 32(8):797-816, 1995). Elementary school students have growing vocabularies and many are learning English as a secondary language or depend on schools to learn academic English. Teachers must have a clear understanding of science vocabulary in order to communicate and evaluate these understandings with students. The present study measured preservice teachers' vocabulary knowledge during a science methods course and documented their use of science vocabulary during peer teaching. The data indicate that the course positively impacted the preservice teachers' knowledge of select elementary science vocabulary; however, use of science terms was inconsistent in microteaching lessons. Recommendations include providing multiple vocabulary instruction strategies in teacher preparation.