Background Following the repair of TOF patients may be left with pulmonary regurgitation and a dilated right ventricle (RV), which in turn can lead to ventricular arrhythmias and sudden death. A prolonged QRS is a predictor of ventricular arrhythmias. However, whether subsequent pulmonary valve replacement (PVR) can reverse QRS‐prolongation is controversial. We hypothesized that changes in QRS duration following PVR are determined by preoperative QRS‐duration and RV volumes Methods A retrospective single‐center cohort study was conducted on 142 post‐TOF repair patients (mean age 25 ± 13 years) who underwent PVR between 1995 and 2019. Information on QRS duration and RV volumes measured by cardiac MRI (available in 83 patients) were collected. A linear mixed model was used to investigate the association between the preoperative QRS duration and RV volumes and the postoperative QRS duration. Results The QRS‐duration following PVR continued to increase in all subjects with a prolonged preoperative QRS‐duration(>160 ms, rate of increase of 0.87 msec ± 0.33 per year; p = .01), markedly raised RV end‐diastolic volume (RVEDV; ≥166 ml/m2, rate of increase of 2.0 msec ± 0.37 per year; p < .01) or RV end‐systolic volume (RVESV; ≥89 ml/m2, rate of increase of 1.25 msec ± 0.43 per year; p = .01). In contrast, in patients with preoperative QRS‐duration <160 msec (p = .16), RVEDV <166 ml/m2 (p = .14), or RVESV < 89 ml/m2 (p = .37), the QRS‐duration did not change significantly when compared to preoperative values. Conclusions In subjects with shorter QRS and smaller RV volumes, QRS duration did not show further prolongation following PVR. While markedly prolonged QRS and increased RV volumes were associated with a small but constant increase in QRS duration despite PVR.