Background: Cochlear implantation is safe and effective in restoring hearing and speech recognition abilities for individuals with severe to profound sensorineural hearing loss. This prospective multicenter clinical trial was conducted to evaluate the safety and effectiveness of a novel cochlear implant (CI) system, the LISTENT LCI-20PI device, in post-lingually deafened individuals. Methods: The LCI-20PI CI system was implanted in 70 individuals 6-68 (27.7 ± 14.0) years old. The safety and effectiveness of the devices were evaluated during a 1-year follow-up. Results: Electrically evoked compound action potential were successfully measured in 98.6% (69/70) of subjects. Electrode impedance was within normal limits of 0.7-20 kOhm in 99.8% of cases. All subjective T/C levels were successfully measured on the selected 12 electrodes of the LCI-20PI recipients at device activation and 1 month, 3 months, 6 months, and 12 months post-activation. The mean open-set monosyllabic-word recognition score (MRS), disyllabic-word recognition score (DRS), and sentence recognition score (SRS) were 28.9 ± 21.0%, 30.3 ± 25.8%, and 36.3 ± 36.3% at 6 months post-activation, and 57.1 ± 21.1%, 69.1 ± 24.4%, and 89.7 ± 21.5% at 12 months post-activation, respectively. Sex, side of the ear implanted, residual hearing, duration of deafness, etiology of deafness, and surgeon did not influence postoperative speech recognition performance. Conclusion: The novel LCI-20PI CI device is safe and effective in post-lingually deafened recipients.