Objective Reports in the literature of treatment with recombinant tissue plasminogen activator following cardiac surgery are limited. We reviewed our experience to provide a case series of the therapeutic use of tissue plasminogen activator for the treatment of venous thrombosis in children after cardiac surgery. The data describe the morbidity, mortality, and clinical outcomes of tissue plasminogen activator administration for treatment of venous thrombosis in children following cardiac surgery. Design The study was designed as a retrospective case series. Setting The study was carried out in a 25-bed cardiac intensive care unit in an academic, free-standing paediatric hospital. Patients All children who received tissue plasminogen activator for venous thrombosis within 60 days of cardiac surgery, a total of 13 patients, were included. Interventions Data was collected, collated, and analysed as a part of the interventions of this study. Measurements and main results Patients treated with tissue plasminogen activator were principally young infants (median 0.2, IQR 0.07-0.58 years) who had recently (22, IQR 12.5-27.3 days) undergone cardiac surgery. Hospital mortality was high in this patient group (38%), but there was no mortality attributable to tissue plasminogen activator administration, occurring within <72 hours. There was one major haemorrhagic complication that may be attributable to tissue plasminogen activator. Complete or partial resolution of venous thrombosis was confirmed using imaging in 10 of 13 patients (77%), and tissue plasminogen activator administration was associated with resolution of chylous drainage, with no drainage through chest tubes, at 10 days after tissue plasminogen activator treatment in seven of nine patients who had upper-compartment venous thrombosis-associated chylothorax. Conclusions On the basis of our experience with administration of tissue plasminogen activator in children after cardiac surgery, tissue plasminogen activator is both safe and effective for resolution of venous thrombosis in this high-risk population.