A quasi-experimental control group pre- and post-test study was used to determine the effect of a Multi-Step Inquiry (MSI) approach on pre-service elementary school teacher's conceptual understanding. The MSI study involved the development of a conceptual workbook, and a Physical Science Concept Inventory. The conceptual workbook has activities that explicitly target students' misconceptions in physical science. The inventory has three categories: forces and motion, heat and temperature, and electricity. Descriptive and inferential statistics were used to interpret the data. Independent t-tests were used to compare the experimental and comparison groups. Further, Cohen's d and Hake's g effect sizes were used to determine the effectiveness of MSI. Results indicated that the MSI approach as an effective teaching strategy for conceptual understanding. As such, the authors have made recommendations for both research and teaching.