Both surgical and percutaneous closures of atrial septal defects have been successful in reversal of atrial dilatation. We compared the effects of surgical and percutaneous transvenous device closure of atrial septal defect on post-operative changes of P-wave duration, PR segment, and PR interval. Electrocardiographic data were prospectively collected from 30 patients following either surgical (n equal to 16) or percutaneous (n equal to 16) repair of atrial septal defects between 2004 and 2010. A cardiologist blinded to the closure technique performed the electrocardiographic analyses. P-wave duration (98.5 plus or minus 15.4 to 86.4 plus or minus 13.2 milliseconds, p-value less than 0.05) and PR interval (162.9 plus or minus 18.5 to 140.6 plus or minus 15.2 milliseconds, p-value less than 0.05) were reduced after percutaneous transvenous device closure. P-wave duration (104.5 plus or minus 24.7 versus 83.2 plus or minus 13.3 milliseconds, p-value less than 0.05) and PR interval (173.2 plus or minus 38.7 versus 144.3 plus or minus 32.0 milliseconds, p-value less than 0.05) were also reduced after surgical closure. PR segment in the percutaneous group was significantly reduced (63.4 plus or minus 14.5 to 52.1 plus or minus 10.8 milliseconds, p-value less than 0.05), but not in the surgical group (68.6 plus or minus 18.7 versus 61.1 plus or minus 24.7 milliseconds). However, the difference in PR segment changes between the two groups was not significant (-11.3 plus or minus 15.0 versus -7.6 plus or minus 20.5 milliseconds, p-value equal to 0.18). Our analysis demonstrates that the changes between the two groups were not different and that both closure techniques reduce P-wave duration, PR segment, and PR interval within 6 months.