Background and Objectives: A cochlear implant (CI) is an effective prosthetic device used to treat severe-to-profound hearing loss. The present study examined cognitive function in CI users by employing a web-based cognitive testing platform, i.e., BrainCheck, and explored the correlation between cognitive function and subjective evaluation of hearing. Subjects and Methods: Forty-two CI users (mean age: 58.90 years) were surveyed in the subjective evaluation of hearing, and 20/42 participated in the BrainCheck cognitive tests (immediate recognition, Trail Making A, Trail Making B, Stroop, digit symbol substitution, and delayed recognition). As controls for cognitive function, young normal-hearing (YNH, mean age=23.83 years) and older normal-hearing (ONH, mean age=52.67 years) listener groups were subjected to Brain-Check testing. Results: CI users exhibited poorer cognitive function than the normal hearing groups in all tasks except for immediate and delayed recognition. The highest percentage of CI users who had “possible” and “likely” cognitive impairment, based on BrainCheck scores (ranging from 0-200), was observed in tests assessing executive function. The composite cognitive score across domains tended to be related to subjective hearing (p=0.07). Conclusions The findings of the current study suggest that CI users had a higher likelihood of cognitive impairment in the executive function domain than in lower-level domains. BrianCheck online cognitive testing affords a convenient and effective tool to self-evaluate cognitive function in CI users.