This is a prospective observational study involving 11 eyes of 11 patients with pseudophakic endothelial failure who underwent human corneal endothelial cell culture (hCEC) injection therapy for endothelial failure. This study aimed to evaluate the long-term five-year postoperative data for these patients. The primary outcome was the change in central endothelial cell density following the hCEC therapy, with secondary outcomes including corneal thickness, best corrected visual acuity (BCVA) and intraocular pressure (IOP) during the five-year postoperative follow-up period. The results found that in 10 of the 11 eyes, normal corneal endothelial function was restored five years after surgery with the mean central corneal endothelial cell density being 1257 cells/mm2. Central corneal thickness was within the normal range (<630 microns) in 10 of the 11 eyes. BCVA was improved in 10 of the 11 eyes, with a visual acuity (VA) recovery of 0.5 or more. Additionally, no increase in IOP was noted in 10 of the 11 eyes. This is the first-in-human trial which supports the use of hCEC injection therapy for corneal endothelial failure. However, further data on larger patient groups is necessary, in particular to compare outcomes with existing treatment modalities such as endothelial grafting (DSAEK/DMEK).