Prolongation of the QTc interval is a predictor of adverse cardiovascular outcomes in patients with end-stage kidney disease undergoing maintenance dialysis. The purpose of our study was to assess change in QTc intervals after kidney transplantation, and to derive insights into the mechanism and consequence of observed changes. A retrospective chart review was performed on 309 kidney transplant recipients to assess QTc interval changes from baseline, recorded 1 day prior to transplant, to 2 days, 2 weeks, 1 month, 3 months, and 6 months post-transplant. Cardiac deaths occurring within the first year after transplantation were assessed. Prolonged QTc was present in 36.6% of the cohort. There was a rapid shortening of mean QTc interval evident as early as 2 days post-transplant [mean QTc decrease of 13.2 ms (p<0.001, 95% CI,-17.9,-8.4)]. This QTc decrease reached a nadir of-32.4 ms (p<0.001, 95% CI,-38.4,-26.3) at 1 month post-transplant, and remained shortened at 6 months post-transplant, [mean QTc decrease of 29.4 ms (p<0.001, 95% CI,-36.4,-22.4)]. Those with pre-transplant QTc prolongation exhibited a more robust mean QTc shortening at all follow-up time points. Delayed graft function was associated with delayed QTc shortening post-transplant. Three out of four patients who suffered cardiac death within the first year post transplantation had QTc prolongation at the time of transplantation and represented 2.7% of those with pre-transplant QTc prolongation. Our study demonstrates a rapid and long-lasting QTc interval shortening after successful kidney transplantation. The prompt shortening, coupled with delayed shortening when graft function is delayed, strongly suggests that prolonged QTc in ESRD patients is the consequence of electrolyte disorders and/or accumulated uremic toxins rather than myocardial injury. Three out of four cardiac deaths in the first year post-transplantation occurred in those patients with pre-transplant QTc prolongation.