The current paper scrutinizes the phonological processes used by an autistic child, in Standard Arabic, via the use of a constraint-based framework of optimality theory. The data of the present study were collected through a picture-naming test. To ensure that the pictures are representative of all standard Arabic phonemes, the researcher designed a test containing 84 pictures representing three intra-word positions (initial, medial, and final). The results reveal that the autistic child grammar is characterized, mainly, with seven phonological processes: sibilant dentalization, de-emphasization, gliding, stopping, nasality spreading, final consonant deletion, and fronting. Autistic children's phonological system is stigmatized by unmarked forms. In terms of optimality theory, treating the phonological problems of autistic children requires demoting the highly ranked unmarked constraints and promoting the lowest-ranked faithfulness constraint.