Researchers and educators continue to explore how to assist students in the acquisition of conceptual understanding of complex science topics. While hypermedia learning environments (HLEs) afford unique opportunities to display multiple representations of these often abstract topics, students who do not engage in self-regulated learning (SRL) with HLEs often fail to achieve conceptual understanding. There is a lack of research regarding how student characteristics, such as prior knowledge and students' implicit theory of intelligence (ITI), interact with SRL to influence academic performance. In this study, structural equation modeling was used to investigate these issues. It was found that prior knowledge and ITI were related to SRL and performance, and that SRL acted as a benevolent moderator, enhancing the positive effects of prior knowledge upon learning, and diminishing the negative effects of having a maladaptive ITI. (Contains 5 tables and 3 figures.)