We study fine-grained stereotypes of LLMs activated by linguistic features representing demographic groups, developing a probe-based framework to extract 235 fine-grained traits (e.g., friendly, uneducated, honest) from model representations of prompts. Using these probes, we conduct two studies analyzing the underlying structure of traits and specific stereotypes of demographic groups. We find that fine-grained trait information is represented in LLMs similarly to coarse stereotype content dimensions (e.g., warmth and competence), and that the latent factors of trait probes (e.g., morality, competence, sociability) largely align with those in the psychology literature (Fiske et al., 2002) despite traits being modeled independently. Finally, we extract LLMs’ associations between traits and demographics signaled through language to surface granular stereotypes encoded in LLMs. We, for example, find that the evaluated models encode associations between African American Language and traits clumsy, uneducated, and criminal. These associations may reinforce harmful stereotypes, with implications for both general dialogue responses and in domains like hiring. Overall, we discuss the need to consider fine-grained traits in stereotype evaluations in order to distinguish stereotypes of out-groups and between models.