Purpose: To demonstrate the importance of speech therapy and hearing aids in the development of the phonological system of a child with hearing loss. Case Report: A 6-year-old, girl child with moderate mixed hearing loss and flat configuration resulting from chronic otitis media participated in this study. She used a hearing aid (HA) and began therapy 4 years ago. The phonological system was evaluated through the Phonological Assessment of Child (PAC) instrument, which focuses on the analysis of phonological processes and distinctive features. Results: Through the instrument, the following substitutions were identified: /s/→/∫/ and /z/→/•/. The data show that the child has the phonological process of posteriorization of fricatives in which are committed the traits [previous] and [high], in which substitutions are a phoneme [+ previous] for a [- previous] and [- high] by a [+ high]. Conclusion: The development of the phonological system of this hearing impaired child is very close to the system used by a hearing child of the same age. The use of hearing aid and speech therapy since the age of 2 contributed greatly to the quality of this development since children with moderate hearing loss have a deficit in temporal resolution and frequency resolution. They have the ability to perceive the voicing of consonants; however, they have difficulty understanding the point and manner of articulation. This interferes with the discrimination between phonemes and leads to omissions and distortions of consonants, which is a common characteristic of hearing-impaired children.