This paper reports on one preservice teacher’s use of the Inquiry-Application Instructional Model (I-AIM) to plan and teach an instructional sequence on photosynthesis to 5th-grade students. Analysis of the preservice teacher’s planned and enacted instructional sequences and interviews shows that the preservice teacher was successful in leveraging the conceptual change but not the inquiry aspects of the I-AIM. The mediators of this preservice teacher’s use of the I-AIM included her approach to teaching science, the curriculum materials she had available, and the meanings she made of the underlying frameworks. Understanding the mediators of preservice teachers’ uses of instructional models can inform teacher educators’ approaches to supporting preservice teachers in using instructional models for organizing science instructional sequences.