PCE is a complication of HSCT that has previously been described in small single-center studies. This study aimed to assess the frequency of, risk factors for, and outcomes of children with a PCE following HSCT across a large multi-center cohort. All patients ≤21 years undergoing first HSCT (1/2005-9/2015) were identified from the Pediatric Health Information System. ICD-9 codes were used to identify patients with a PCE during or following the transplant encounter. Multivariable modeling assessed risk factors for developing a PCE and assessed the impact of PCE on patient outcome. Of 10 455 included patients, 739 (7.1%) developed a PCE (median 69 days post-HSCT, interquartile range 33-165 days). PCE developed more commonly in allogeneic vs autologous HSCT recipients (9.1% vs 2.9%, P < .001). Among allogeneic HSCT recipients, independent risk factors for PCE included thrombotic microangiopathy (AHR 2.94, 95% CI 2.16-4.00), heart failure (AHR 2.07, 95% CI 1.61-2.66), PCE pre-HSCT (AHR 1.92, 95% CI 1.19-3.09), arrhythmia (AHR 1.76, 95% CI 1.44-2.16), graft-versus-host disease (AHR 1.31, 95% CI 1.05-1.62), female sex (AHR 1.28, 95% CI 1.07-1.52), and malignancy (AHR 1.28, 95% CI 1.02-1.60). Allogeneic HSCT patients with PCE demonstrated worse survival than those without PCE (5-year survival 50.8% vs 76.9%, P < .001). PCE was independently associated with mortality (AHR 1.96, 95% CI 1.62-2.37) following allogeneic HSCT and was not impacted by pericardial intervention. PCE occurs more commonly in patients following allogeneic (vs autologous) HSCT and is associated with inferior outcomes.