In the past decade, reform efforts in science education have increasingly attended to engaging students in scientific practices such as scientific modeling. Engaging students in scientific modeling can help them develop their epistemologies by allowing them to attend to the roles of mechanism and empirical evidence when constructing and revising models. In this article, we present our in-depth case study of how two fifth graders--Brian and Joon--who were students in a public school classroom located in a Midwestern state shifted their epistemologies in modeling as they participated in the enactment of a technologically enhanced, model-based curriculum unit on evaporation and condensation. First, analyses of Brian's and Joon's models indicate that their epistemologies in modeling related to explanation and empirical evidence shifted productively throughout the unit. Additionally, while their initial and final epistemologies in modeling were similar, the pathways in which their epistemologies in modeling shifted differed. Next, analyses of the classroom activities illustrate how various components of the learning ecology including technological tools, the teacher's scaffolding remarks, and students' collective activities and conversations, were marshaled in the service of the two students' shifting epistemologies in modeling. These findings suggest a nuanced view of individual learners' engagement in scientific modeling, their epistemological shifts in the practice, and the roles of technology and other components of a modeling-oriented learning environment for such shifts.