A cochlear implant (CI) can partially restore hearing in patients with severe to profound sensorineural hearing loss. However, the large outcome variability in CI users prompts the need for more objective measures of speech perception performance. Electrophysiological metrics of CI performance may be an important tool for audiologists in the assessment of hearing rehabilitation. Utilizing electroencephalography (EEG), it may be possible to evaluate speech perception correlates such as spectral discrimination. The mismatch negativity (MMN) of 10 CI subjects was recorded for stimuli containing different spectral densities. The neural spectral discrimination threshold, estimated by the MMN responses, showed a significant correlation with the behavioral spectral discrimination threshold measured in each subject. Results suggest that the MMN can be potentially used to obtain an objective estimate of spectral discrimination abilities in CI users.