SCIENTIFIC Science simulations are interactive tasks that allow students to explore a science phenomenon and engage in science inquiry by collecting data and testing hypotheses. Though simulations are increasingly being used in assessment, little is known about how students’ metacognition, such as confidence in a response and ratings of understanding of a simulated concept, relate to within-simulation assessment behaviors. The study explored the relationship between students’ metacognition and their science inquiry behaviors in a simulation assessment. During the simulation participants interacted with a concentration of solutions simulation to answer questions about saturation. Participants could manipulate variables in the simulation, such as the amount of solute and solvents added to a container, and create and modify data tables. Interactive inquiry behaviors, test performance, ratings of understanding of concentration, and confidence in test responses were measured. Results showed that overconfidence was related to reduced inquiry and poorer assessment performance. (PsycINFO Database Record (c) 2018 APA, all rights reserved)