Epistemic criteria are the standards used to evaluate scientific products (e.g., models, evidence, arguments). In this study, we analyzed epistemic criteria for good models generated by 324 middle-school students. After evaluating a range of scientific models, but before extensive instruction or experience with model-based reasoning practices, students generated lists of criteria of good scientific models. Students' individual lists of criteria were compared to expert criteria, identified by philosophers of science, and with findings from previous research on students' understanding of modeling. The most commonly listed criteria referred to the clarity, pictorial form, and explanatory function of models. Almost a quarter of the students included criteria relating to model fit with evidence. Students' criteria provided insights into their understanding of the explanatory and descriptive goals of models; the constitutive, communicative, and epistemic features of models; and the role of evidence in supporting models. Collectively, students demonstrated familiarity with a wide range of modeling ideas that can be leveraged in instruction to promote deeper understandings of the modeling practice. We argue that inquiry-based science instruction should include a strong emphasis on epistemic criteria. (Contains 1 table.)