Acute peritoneal dialysis (PD) is the preferred therapy for renal replacement in children with post-diarrheal hemolytic uremic syndrome (D+ HUS), but peritonitis remains a frequent complication of this procedure. We reviewed data from 149 patients with D+ HUS who had undergone acute PD with the aim of determining the prevalence and risk factors for the development of peritonitis. A total of 36 patients (24.2%) presented peritonitis. The median onset of peritonitis manifestations was 6 (range 2-18) days after the initiation of dialysis treatment, and Gram-positive microorganisms were the predominant bacterial type isolated (15/36 patients). The patients were divided into two groups: with or without peritonitis, respectively. Univariate analysis revealed that a longer duration of the oligoanuric period, more days of dialysis, catheter replacement, stay in the intensive care unit, and hypoalbuminemia were significantly associated to the development of peritonitis. The multivariate analysis, controlled by duration of PD, identified the following independent risk factors for peritonitis: catheter replacement [p = 0.037, odds ratio (OR) 1.33, 95% confidence interval (CI) 1.02-1.73], stay in intensive care unit (p = 0.0001, OR 2.62, 95% CI 1.65-4.19), and hypoalbuminemia (p = 0.0076, OR 1.45, 95% CI 1.10-1.91). Based on these findings, we conclude that the optimization of the aseptic technique during catheter manipulation and early nutritional support are targets for the prevention of peritonitis, especially in critically ill patients.