National and state science learning standards urge K-12 educators to offer authentic Science, Technology, Engineering, and Mathematics learning experiences. One way to fulfill this goal is to prepare preservice science teachers to integrate computer science skills, such as coding, into science education learning contexts that can benefit from it. This study implemented Coding in Scientific Modeling Lessons (CS-ModeL) in a science teacher education course. CS-ModeL is the name of an instructional module and of an online tool, and they aim to support preservice science teachers' use of coding in scientific modeling and lesson design. Preservice teachers used block-based coding to create science simulations, performed analogous physical experiments, and designed lessons in which they support scientific modeling with coding. This mixed methods study investigated if and how participation in CS-ModeL affected preservice teachers' epistemological understanding of scientific models and modeling along with their understanding of computer science concepts. This study also examined coding-enhanced scientific modeling activities in their designed lessons. Results showed an overall improvement in participants' epistemological understanding of models and modeling, and in their understanding of computer science concepts. Participants' lessons featured activities in which block-based coding simulations are used either as a research tool or as an exploration tool. Additionally, most lessons targeted computer science practices, but not concepts. It was also found that participants' lessons were not aligned with their epistemological understanding of models and modeling. Study limitations, implications for research and practice, and directions for future research are discussed.