Cochlear reimplantation is becoming more common; however, some patients do not achieve the expected outcomes. There is limited evidence regarding cochlear reimplantation-related developmental delays. This study aimed to (1) systematically compare the performance of children with cochlear reimplantation to those with primary cochlear implants using behavioral and EEG measures and (2) identify the influencing factors.This cross-sectional study was conducted at 2 tertiary medical centers specializing in audiology and cochlear implantation from April 2023 to February 2024. The study included 51 children with cochlear reimplantation and 51 with primary cochlear implants. Participants were matched based on age, sex, the unaided pure-tone average, and intervention modality. Furthermore, the participants underwent audiometry, auditory function and speech assessments, grammatical comprehension test, quality-of-life assessment, cognitive evaluation, and EEG test (mismatch negativity). Multiple linear regression models were used to assess associations between the outcomes and demographic, surgical, and rehabilitation factors.The study included 102 children: 51 with cochlear reimplantation (mean age: 11.24 yr, SD: 3.43) and 51 with primary cochlear implants (mean age: 11.64 yr, SD: 3.20), matched by age and sex (51% male). Children who had undergone cochlear reimplantation performed significantly worse than their primary cochlear implant counterparts in both behavioral and EEG measures. They showed poorer grammatical comprehension, lower quality of life scores related to cochlear implant use, longer multifeature mismatch negativity latencies, more negative alpha power changes, and weaker alpha-band functional connectivity during monosyllable discrimination, indicating slower processing and a greater cognitive load. Multiple linear regression analysis revealed that the auditory age, cognitive status, intervention modality, residential area, caregiver type, parental education level, and language environment influenced children's performance after cochlear reimplantation.Cochlear reimplantation can delay grammatical comprehension, worsen quality of life, and worsen auditory discrimination. These effects can be mitigated by early implantation, longer cochlear implant use, cognitive stimulation, bilateral or bimodal intervention, urban living, high-quality parental engagement, and a Mandarin-speaking environment.Copyright © 2025 The Authors. Ear & Hearing is published on behalf of the American Auditory Society, by Wolters Kluwer Health, Inc.