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Introduction: The ictal interictal continuum (IIC) is a common EEG pattern identified in critically ill adults. The IIC has not been systematically studied in critically ill children. We report the incidence of the IIC in the pediatric intensive care unit (PICU). We then compare IIC patterns to periodic and rhythmic patterns (PRP) not meeting IIC criteria looking for associations with cerebral injury, electrographic seizures (ES), and in-hospital mortality. Methods Prospective study of patients admitted to the PICU at Children’s National Hospital from July 2021 to January 2023. All patients with continuous EEG were screened for PRP. American Clinical Neurophysiology Society standardized critical care EEG terminology for the IIC were applied to each PRP. We excluded patients with epilepsy and/or remote cerebral injury. Associations between IIC and PRP not meeting IIC criteria, with clinical and EEG variables were calculated using odds ratios. Results Of 201 patients, 21% (42/201) had a PRP, and 12% (24/201) met IIC criteria. Among patients with an IIC pattern, the median age was 3.4 years (IQR 0.6–12). Sixty-seven percent (16/24) met a single IIC criterion, while the remainder met two criteria. ES were identified in 83% (20/24) and cerebral injury in 96% (23/24) of patients with IIC patterns. When comparing patients with IIC patterns to those with PRP not qualifying as an IIC pattern, both patterns were associated with cerebral injury (IIC OR 26(95% CI 3.4–197) p = 0.0016 vs. PRP OR 3.5(95% CI 1.1–11), p = 0.03), however only the IIC was associated with ES (OR 121(95% CI 33–451), p < 0.0001); vs PRP (OR 1.3(0.4-5), p = 0.7). Conclusions The IIC is seen in over 10% of critically ill children and suggests cerebral injury. The independent impact of the IIC on secondary brain injury requires further study.