Importance If the success of Descemet membrane endothelial keratoplasty (DMEK) is not affected by whether the donor has diabetes, then the donor pool should expand. Objective To determine whether the 1-year DMEK success rate is affected by the presence of diabetes in the donor. Design, Setting, and Participants This was a multicenter, double-masked, randomized clinical trial conducted from February 2022 to July 2025 at 28 clinical sites (46 surgeons), with donor corneas provided by 13 eye banks in the US. Included in the study were individuals undergoing low to moderate risk DMEK (95% for Fuchs endothelial corneal dystrophy). Study data were analyzed from April to September 2025. Intervention DMEK performed with a cornea from a donor without or with diabetes, assigned using a minimization procedure (comparable with randomization) to achieve an approximate 2:1 distribution, respectively. Main Outcomes and Measures Graft success at 1 year Results A total of 1097 individuals (1421 study eyes; median [IQR] age, 71 [66-76] years; 631 female [57.5%]) were included in the study. The 1-year cumulative probability of graft success was 96.3% (95% CI, 95.0%-97.5%) among 912 study eyes (64.2%) receiving tissue from donors without diabetes and 97.1% (95% CI, 95.5%-98.4%) among 509 study eyes (35.8%) receiving tissue from donors with diabetes (difference between groups = 0.7 percentage points; 95% CI, −1.2 to 2.6; P = .63). The 1-year cumulative probability of graft success was 96.5% (95% CI, 93.6%-98.9%) in the mild donor diabetes severity subgroup (n = 173) and 97.3% (95% CI, 95.4%-98.8%) in the moderate to severe donor diabetes severity subgroup (n = 336), using a diabetes severity rating scale based on medical history. The rates of primary donor failure, early failure related to surgical complications, and subsequent failure were as follows: 2.5% (23 of 912), 0.7% (6 of 912), and 0.3% (3 of 912), respectively, in recipients of tissue from a donor without diabetes, and 2.6% (13 of 509), 0.4% (2 of 509), and 0%, respectively, among recipients of tissue from a donor with diabetes. There were no failures due to graft rejection. Conclusions and Relevance The 1-year success rate in eyes undergoing DMEK with successfully prepared tissue was very high regardless of donor diabetes status. These results, supported by the separately reported finding that endothelial cell loss and cornea morphometry after 1 year were not affected by donor diabetes status, provide strong support for having no restrictions on the use of tissue from donors with diabetes for DMEK. Trial Registration ClinicalTrials.gov Identifier: NCT05134480