Abstract OBJECTIVES Timing of pulmonary valve replacement (PVR) remains one of the most heavily debated topics in congenital cardiac surgery. We aimed to analyse the temporal evolution of QRS duration before and after PVR. METHODS We included 158 consecutive patients who underwent PVR after previous correction with transannular patch. All 3549 available serial standard 12-lead surface QRS measurements of 158 (100%) patients were analysed with linear mixed-effect modelling. RESULTS PVR was performed at a mean age of 28.0 ± 10.7 years, 23.4 ± 8.4 years after correction. Hospital survival was 98.1%. A longer time interval between ToF correction and PVR (P < 0.001), and an older age at correction (P = 0.015) were predictive of progressive QRS prolongation after PVR. Women on average had a shorter QRS duration (P = 0.005) after PVR. The model predicted that in patients corrected early (model age 0.5 years), PVR within 17 years after correction leads to narrowing or stabilization of QRS width. PVR beyond 17 years was associated with prolongation of QRS duration. In a patient corrected late (model age 5 years), PVR has to be performed within 15 years after correction to prevent prolongation. Finally, a longer time period between correction and PVR was associated with an increased hazard of cardiac death (hazard ratio 1.097, 95% confidence interval 1.002–1.200). CONCLUSIONS Prolongation of QRS duration after PVR was associated with a longer time between correction and PVR, older age at correction and male sex. Prevention of progressive QRS prolongation by earlier PVR can potentially reduce the hazard of adverse events after PVR.