To evaluate the incidence, predictive factors and prognostic value of new-onset persistent left bundle branch block (NOP-LBBB) in patients undergoing sutureless surgical aortic valve replacement (SU-SAVR). A total of 329 consecutive patients without baseline conduction disturbances or previous permanent pacemaker implantation (PPI) who underwent SU-SAVR with the Perceval valve (LivaNova Group, Saluggia, Italy) in two centres from 2013 to 2019 were included. Patients were on continuous ECG monitoring during hospitalisation and 12-lead ECG was performed after the procedure and at hospital discharge. NOP-LBBB was defined as a new postprocedural LBBB that persisted at hospital discharge. Baseline, procedural and follow-up clinical and echocardiography data were collected in a dedicated database. New-onset LBBB was observed in 115 (34.9%) patients, and in 76 (23.1%) persisted at hospital discharge. There were no differences in baseline and procedural characteristics between patients with (n=76) and without (n=253) NOP-LBBB. After a median follow-up of 3.3 years (2.3-4.4 years), patients with NOP-LBBB had a higher incidence of PPI (14.5% vs 6.3%, p=0.016), but exhibited similar rates of all-cause mortality (19.4% vs 19.2%, p=0.428), cardiac mortality (8.1% vs 9.4%, p=0.805) and heart failure readmission (21.0% vs 23.2%, p=0.648), compared with the no/transient LBBB group. NOP-LBBB was associated with a decrease in left ventricular ejection fraction (LVEF) at 1-year follow-up (delta: -5.7 vs +0.2, p<0.001). NOP-LBBB occurred in approximately a quarter of patients without prior conduction disturbances who underwent SU-SAVR and was associated with a threefold increased risk of PPI along with a negative impact on LVEF at follow-up. © Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.