Purpose: To evaluate the discriminant accuracy of a grammatical measure for the identification of language impairment (LI) in Latino English-speaking children. Specifically, the study examined the diagnostic accuracy of the Test of English Morphosyntax (E-MST; Pena, Gutierrez-Clellen, Iglesias, Goldstein, & Bedore (n.d.) to determine (a) whether use and exposure to Spanish had an effect on the performance of bilingual children compared with monolingual Latino children and (b) whether dialectal differences within Latino English speakers might result in performance differences and a greater incidence of misclassifications for children from Caribbean English backgrounds. Method: One hundred and eleven children (i.e., 59 children with typical language development and 52 children with LI) were sampled from the Southwest and Northeast regions of the U.S. Southwestern children were of Mexican origin. Children from the Northeast were from Puerto Rican or Dominican backgrounds. Linear discriminant analyses evaluating group classifications on the basis of the E-MST were performed on exploratory and confirmatory data sets across 3 groups: Southwestern English-only proficient (SW EP) children, Southwestern English-dominant bilingual (SW EDB) children, and Northeastern (NE) children. Results: Results of the exploratory discriminant analyses indicated good sensitivity for the SW EP children. The discriminant functions derived from the exploratory analysis were able to predict group membership in confirmatory discriminant analyses with fair sensitivity and good specificity for the SW EDB children and with fair sensitivity but poor specificity for the NE children. Children who were English-dominant bilingual were not more likely to be misclassified compared with their English-only proficient peers. However, nonmainstream English dialect differences appeared to affect classification accuracy and resulted in a greater number of misclassifications for the NE children with typical language development. Conclusion: The measure seems to be suitable for identifying LI in SW children who are exposed to Spanish and/or who are English-dominant bilingual. Additional assessment tools will be needed to rule out the disorder in children who are exposed to African American or Caribbean English dialects.