Purpose: This study was designed to examine the relationships among minority dialect use, language ability, and young African American English (AAE)-speaking children's understanding and awareness of Mainstream American English (MAE). Method: Eighty-three 4- to 8-year-old AAE-speaking children participated in 2 experimental tasks. One task evaluated their awareness of differences between MAE and AAE, whereas the other task evaluated their lexical comprehension of MAE in contexts that were ambiguous in AAE but unambiguous in MAE. Receptive and expressive vocabulary, receptive syntax, and dialect density were also assessed. Results: The results of a series of mixed-effect models showed that children with larger expressive vocabularies performed better on both experimental tasks, relative to children with smaller expressive vocabularies. Dialect density was a significant predictor only of MAE lexical comprehension; children with higher levels of dialect density were less accurate on this task. Conclusions: Both vocabulary size and dialect density independently influenced MAE lexical comprehension. The results suggest that children with high levels of nonmainstream dialect use have more difficulty understanding words in MAE, at least in challenging contexts, and suggest directions for future research.