Purpose Individuals with Down syndrome (DS) often receive speech-language therapy services starting in infancy or toddlerhood. When providing speech-language therapy services for children with DS, speech-language pathologists (SLPs) need to consider the impact of other developmental and comorbid disorders that can affect language development, such as the presence of a dual diagnosis of DS and autism spectrum disorder (DS + ASD). The prevalence rate of ASD in DS is ~20%, which is higher than in the general population. Method This clinical focus article aims to provide SLPs with additional knowledge about DS + ASD to improve service delivery and support parents' ability to advocate for their child with confirmed or suspected DS + ASD. This is accomplished by summarizing the current evidence base on the presence of ASD in DS and discussing implications of a DS + ASD diagnosis for clinical practice with SLPs. Conclusions SLPs play a key role in supporting families of those with DS + ASD by advocating and educating. By understanding the unique profiles of strengths and weaknesses of individuals with DS + ASD, SLPs can provide appropriate service delivery (i.e., treatment and intervention approaches) and advocacy for their clients and their families.