Children with Developmental language disorder (DLD) have particular difficulty learning language despite otherwise general normal development. When school age bilingual children struggle with language, a common question is if the difficulties they present reflect lack of ability or lack of language experience. To address the question of identification of DLD in the context of bilingualism, we explore the diagnostic accuracy of measures administered in two languages. The Bilingual English Spanish Assessment Middle Extension (BESA-ME) assesses semantics and morphosyntax and the Test of Narrative Language (TNL) assesses comprehension and production of narratives. These measures were administered to 112 second graders (19 with DLD) and 64 fourth graders (7 with DLD). We explored the classification accuracy of each of these measures alone and in combination using receiver operator characteristic (ROC) curve analysis. The ROC curve illustrates diagnostic classification of a measure at various cutpoints. We compared the extent to which measures in English, Spanish, or best language account for area under the (ROC) curve. Discriminant function analysis using the best indicator (Spanish, English, best language) from each type of measure (semantics, morphosyntax, narrative) in combination demonstrate classification accuracy above 80%. Morphosyntax in the best language was the strongest predictor of DLD for second grade children. In fourth grade, the three measures contributed more equally in predicting DLD.