This study explored pre-service teachers' conceptual understanding and performance on science process skills. A sample comprised 91 elementary pre-service teachers at a university in the Midwest of the USA. Participants were enrolled in two science education courses; introductory science teaching methods course and advanced science methods course. Data were collected through a questionnaire. Results showed that pre-service teachers had limited conceptual understanding of science process skills. On the other hand, they had higher performance on the science process skills. Whilst majority of the participants were unable to provide correct definitions of the science process skills, they performed well on the test that involved novel situations of the process skills. The findings have implications for science teaching, learning and teacher education. (Contains 8 tables.)