Recent research has focused on evaluating the relation between mindset and reading achievement. We used exploratory factor mixture models (E-FMMs) to examine the heterogeneity in reading achievement and mindset of 650 fourth graders with reading difficulties. To build E-FMMs, we conducted confirmatory factor analyses to examine the factor structure of scores of (a) mindset, (b) reading, and (c) mindset/reading combined. Our results indicated (a) a 2-factor model for mindset ("General Mindset vs. Reading Mindset"), (b) a 2-factor model for reading ("Word Reading vs. Comprehension"; four covariances), and (c) a combined model with significant correlations across mindset and reading factors. We ran E-FMMs on the combined model. Overall, we found three classes of students. We situate these results within the existing literature and discuss implications for practice and research.