Purpose: The intent of this article is to explain the complexity of the diagnosis of attention-deficit/hyperactivity disorder (ADHD) and developmental language disorder (DLD) in multilingual (ML) children and adolescents and to offer strategies for speech-language pathologists charged with diagnosis of language impairment in these children. Although both ADHD and DLD are common neurobehavioral disorders that exist across cultures, it can be difficult to diagnose MLs who are learning a second language (L2) and are not part of the mainstream culture because behavioral and language characteristics of both ADHD and DLD overlap with characteristics of L2 learning. As a result of this overlap of characteristics, ML children are both overidentified and underidentified for special education services. We describe the nature of the overlapping characteristics of ADHD, DLD, and L2 learning and offer a number of strategies that have evidence for their usefulness in the assessment of ML children. Conclusions: There is no quick and easy way to diagnose ADHD and DLD in ML children and adolescents. Clinicians must employ a convergent evidence approach, ideally using multiple strategies for evaluation including observations of the child in different contexts, interviewing caregivers and teachers (as well as the child), and administering formal and informal assessments. Clinicians should be alert to the possibility that L2 children's performance may be influenced by trauma associated with their migrant or refugee experiences and the stress of expectations in an unfamiliar environment, which overloads their working memory.