Background Atrioventricular septal defect (AVSD) has an incidence of 4–5.3 per 10.000 live births and is associated with Down syndrome (DS). Data on arrhythmias and sudden cardiac death (SCD) after AVSD correction is scarce. Aim To analyse the incidence of post-operative arrhythmias and SCD after AVSD correction and explore risk factors. Methods This is a retrospective multicenter study including patients after biventricular AVSD correction. Univariate and multivariate analyses were performed to explore risk factors. Results A total of 415 patients were included with a mean follow-up duration of 9 years (range; < 30 days–47 years). Early post-operative SVTs were documented in 33 patients (8%) and late post-operative SVTs in 15 patients (3.6%). Non-syndromic AVSD (p = 0.022, HR = 2.64; 95% CI = 1.15–6.04) and cAVSD (p = 0.005, HR = 3.7; 95% CI = 1.39–7.51) were independent risk factors for early post-operative SVTs and significant more late post-operative SVTs occurred in non-syndromic patients (p = 0.016, HR = 6.38; 95% CI = 1.42–28.71) and in pAVSD (p = 0.045, HR = 3.703; 95% CI = 1.03–13.32). Fifteen patients (3.6%) received a pacemaker. Non-syndromic AVSD (p = 0.008, HR = 15.82; 95% CI = 2.04–122.47), pAVSD (p = 0.017, HR = 6.26; 95% CI = 1.39–28.28) and re-operation (p = 0.007, HR = 4.911; 95% CI = 1.54–15.64) were independent risk factors for postoperative pacemaker implantation. Late life-threatening ventricular arrhythmias and SCD occurred in 0.5% and 1.7% respectively. Conclusion There is good long-term survival after AVSD correction and incidence of SCD is low. Non-syndromic AVSD and cAVSD are independent risk factors for early post-operative SVTs. Non-syndromic AVSD patients have significant more early 3rd degree AVB and late post-operative SVTs. Non-syndromic patients with partial AVSD who have undergone reoperation have a significant higher risk of pacemaker implantation.