In this study, we sought to examine the influence of a 12 week design-based elective Science, Technology, Engineering, and Mathematics (STEM) course on pre-service chemistry teachers' content knowledge, STEM conceptions, and engineering and engineering design views. To attain the goals determined, we utilized five STEM activities starting with a daily-life problem and an iterative engineering design process to solve the problem. A chemistry test with 11 two-tier items, and interviews focusing on STEM and engineering conceptions were administered at the beginning and at the end of the course. Moreover, a reflection paper was collected after each activity. Eight junior pre-service chemistry teachers participated in the study voluntarily. Deductive and inductive data analyses were used to investigate the influence of the course on participants' content knowledge, STEM conceptions, and engineering and engineering design views. The results revealed that the design-based STEM course helped pre-service teachers deepen their content knowledge. Additionally, most of the participants defined integrated STEM education as an acronym (n = 6) and very few mentioned the interdisciplinary dimension of STEM education superficially at the beginning (n = 3). At the end, they mentioned interdisciplinary nature as connecting at least two dimensions of STEM, and they emphasized engaging in real-world problems, designing a product or process and inquiry-based and/or problem-based learning. Regarding engineering and engineering design views, a similar development was observed. Although their views were undeveloped or underdeveloped at the beginning, they enriched their views and mentioned defining criteria, creativity and integration to science and mathematics that are characteristics of engineering and design processes. Implications for including STEM courses in pre-service teacher education programs were provided.