Elicited student mental models reveal students’ understanding of a given system as well as their ability to communicate knowledge of that system to others. Understanding how students form and developmental models of systems is critical to the progress of engineering education. In this work, graduate students’ mental models of common household products are measured before and after instruction on functional modeling and functional decomposition. These mental models are measured using previously published, but still developing mental model instruments. The included systems are a hair dryer, clothes dryer, and vacuum cleaner with accompanying scoring rubrics. Results show statistically significant improvements on average mental model rubric scores on all three given systems after the functional modeling intervention. These results suggest that curriculum content on functional modeling and decomposition likely improves students’ mental models of engineering systems and their ability to communicate their knowledge about those systems. As we improve our understanding of how students form, change, and communicate their mental models of engineering systems, educators can shape curriculum to facilitate the skills necessary for comprehensive systems understanding.