Introduction: Literature regarding the different degrees of hearing loss in patients with Cornelia de Lange syndrome (CDLS) reports that half of the affected patients exhibit severe to profound sensorineural hearing loss. We present the first pre-school child with CDLS who underwent cochlear implantation for congenital profound sensorineural hearing loss.Case Report: A 3-year-old boy with CDLS underwent unilateral cochlear implantation for bilateral profound sensorineural hearing loss. He had characteristic facial features, bushy eyebrows and synophrys, limb anomalies, growth and mental retardation. Based on the results of postoperative speech perception and production tests, his gain in language skills and expressive vocabulary was modest. However, a cochlear implantation had a significant effect on auditory development, in terms of making him aware of sound localization and the different types of environmental sound.Conclusion: Criteria for cochlear implantation are expanding and now include children with disabilities in addition to deafness, such as those with CDLS. Profoundly hearing-impaired children affected by borderline mental retardation should be considered as potential candidates for cochlear implantation.