Nonmainstream American English, or dialect, among children may have important implications for reading research and practice. However, much of the research involving relations between dialect and literacy has analyzed dialect use in only one context and has omitted students with speech, language, and learning disabilities. Consequently, we examined dialect use in an oral narrative and two writing samples in relation to concurrent and longitudinal reading outcomes in a diverse sample of students, including those with diagnosed disabilities. Overall, most students used features of dialect in oral and written language. Dialect use was significantly and negatively predictive of reading outcomes the same year and 2 years later. Moderator analyses indicated a similar relationship between dialect use and reading for students with speech, language, and learning disabilities, suggesting that students with these disabilities who also use dialect may be at increased risk for reading difficulties. Implications for practice and future research are provided.