Down syndrome is the most common genetic syndrome of intellectual disabilities with a distinct linguistic profile. Language research so far has come mainly from the English language, a language with different syntax and morphology from many other languages, including Greek, indicating a paucity of research findings in the Greek language. Given the rich morphology and distinct syntactic characteristics of the Greek language, the present study evaluated the performance of children with Down syndrome (N = 45) who are native Greek speakers in syntax and morphology and compared it with the performance of children with typical development (N = 45) matched for chronological age. The paper also analysed the items of each task in terms of the performance of the two groups in subject-verb agreement, noun conversion from singular to plural, and verb conversion from present to past and future tenses. All children were tested in four subscales of a standardized test, including morphosyntactic comprehension, morphosyntactic completion and articulation (parts 1 and 2). The results showed that children with Down syndrome lag behind in syntax and morphology compared with children of typical development and present difficulties in specific aspects of morphology and syntax inherent in the Greek language.