Background: Diabetes mellitus worsens outcomes in patients suffering from heart disease undergoing cardiac procedures. Objectives: To investigate the impact of diabetes in patients undergoing mitral transcatheter edge-to-edge repair (M-TEER). Methods: 1118 patients treated with M-TEER for functional (FMR) and degenerative (DMR) mitral regurgitation (MR) between 2010 and 2021 were analyzed using the combined endpoint of death/rehospitalization for heart failure (HFH). Results: Among diabetics (N = 306; 27.4%), comorbidities such as coronary artery disease (75.2% vs. 62.7%;p< 0.001) and progressed (stage III/IV) chronic kidney disease (79.5% vs. 72.6%;p= 0.018) were more frequent. The rate of FMR was higher in diabetics (71.9% vs. 64.5%;p< 0.001). The combined endpoint occurred more frequently in diabetics (40.2% vs. 35.6%; log-rank = 0.035). While no difference was observed in FMR patients (36.8% vs. 37.6%; log-rankp= 0.710), rates of the combined endpoint differed significantly between diabetics and non-diabetics in DMR patients (48.8% vs. 31.9%; log-rankp= 0.001) only. However, diabetes did neither predict the combined endpoint in the overall (OR: 0.97; 95% CI 0.65–1.45;p= 0.890) nor in the DMR cohort (OR: 0.73; 95% CI 0.35–1.51;p= 0.389). Among diabetics treated with M-TEER, troponin (OR: 2.32; 95% CI 1.3–3.7;p= 0.002) and estimated glomerular filtration rate (OR: 0.52; 95% CI 0.3–0.88;p= 0.018) independently predicted the combined endpoint. Conclusions: Diabetes is associated with adverse outcomes after M-TEER, particularly in DMR patients. However, diabetes does not predict the combined endpoint. In diabetics undergoing M-TEER, biochemical markers associated with organ function and damage independently predict the combined endpoint of death and rehospitalization.