Hypernasality is a commonly perceived characteristic of speech in deaf adults and children, but the mechanism of this abnormal nasal resonance is poorly understood. The impact of cochlear implantation on nasalance measures in children with severe auditory deprivation has not been previously reported. We conducted a study of nasality in 6 deaf children who had undergone cochlear implantation. Voice recordings were obtained before surgery and 6 months after activation of the implants. The MacKay-Kummer SNAP Test—which consists of a syllable-repetition subtest and a picture-cued subtest—was used to obtain nasalance scores for oral (bilabial, alveolar, velar, and sibilant) and nasal phonemes. Before cochlear implantation, mean nasalance scores were significantly higher than normal during the production of oral phonemes for both subtests (p ≤ 0.05). Six months after activation, the nasalance measures for all components of the syllable-repetition subtest had been restored to within 1 standard deviation of normal. For all oral phonemes of the picture-cued subtest, the elevated nasalance scores were consistently lower after cochlear implant activation, although the difference was statistically significant only for velar tasks. Nasalance scores for nasal phonemes were within 1 standard deviation of normal both before and after implant activation. Our study showed that cochlear implantation partially corrects elevated nasalance measures. Disturbances in nasal resonance may be caused in part by the inability of deaf speakers to monitor velopharyngeal valving with auditory feedback. The trend toward improved nasalance scores after implantation highlights the role of auditory feedback in monitoring velopharyngeal function. Visual biofeedback may be required to further normalize hypernasal speech in profoundly deaf children.