Abstract Introduction Sodium-glucose cotransporter type 2 inhibitors (SGLT2i) have been associated with improved prognosis in patients with heart failure; however, their impact on atrial arrhythmic (AA) and ventricular arrhythmic (VA) events is not fully understood. Methods Retrospective multicentric study of heart failure patients with implantable cardiac defibrillator device (ICD) from 2015 to 2020 with or without cardiac resynchronization therapy (CRT) receiving SGLT2 inhibitors. Device-registered arrhythmic events were analyzed and compared in two time periods for each patient: one year before and one year after starting SGLT2i. Relevant VA were defined as the occurrence of any sustained VT (SVT) (>30 seconds), ventricular fibrillation (VF), or appropriate therapy (antitachycardia pacing or shock). All VA included all the relevant VA and the occurrence of non-sustained ventricular tachycardia (NSVT). AA included atrial fibrillation (AF) burden, and episodes of more than 24 hour of AF. Results A total of 195 patients (66.8 [61.3-73.1] years, 18.5% women) were included. A reduction was observed in the percentage of patients with any VA (pre: 52.3% vs post: 30.3%; P < 0.001) and clinically relevant VA (excluding NSVT) (pre: 21.5% vs post 8.7%; P < 0.001) in the post-SGLT2i period. There was also a reduction in the number of episodes per patient/year of NSVT (pre: 2 (1-5) vs post: 1 (0-2); P < .001), and SVT (pre: 1 (1-3) vs post: 0 (0-2); p = 0.046). This protective effect was also observed after controlling confusion factors (Any VA: OR 0.35 (0,24-0,50); p<0.001 and relevant VA: OR 0.30 (0,17-0,52); p<0.001). However, no differences were observed in the prevalence of AA (24.7% vs 18.8%; P = 0.117) or the burden of atrial fibrillation (pre: 0% (0-0.1) vs post 0% (0-0); p = 0.097). Conclusions Following the initiation of SGLT2i treatment, a reduction in the percentage of patients with relevant VA was observed. However, this effect was not observed for AA.Figure 1Figure 2