Diabetes mellitus complicated by mixed diabetic ketoacidosis and hyperglycemic hyperosmolar syndrome presents a special challenge to physicians. There is no standard protocol for the management of mixed hyperglycemic hyperosmolar syndrome and diabetic ketoacidosis in children. The commonest cause of neurological deterioration during an episode of diabetic ketoacidosis is cerebral edema, whereas hyperosmolality often leads to thrombosis. The risks for these complications are further increased in diseases associated with vasculopathies. We present the first case of complex cerebral arteriovenous thrombosis leading to stroke in a child with Adams-Oliver syndrome, a genetic condition that is associated with abnormal vasculogenesis. He presented with new-onset double diabetes complicated by a combination of diabetic ketoacidosis and hyperglycemic hyperosmolar syndrome. Magnetic resonance imaging, magnetic resonance angiography, and magnetic resonance venography provided evidence for an ischemic stroke. Children and adolescents who present with a combination of hyperglycemic hyperosmolar syndrome and diabetic ketoacidosis should be monitored for neurologic deficits and must be investigated for both stroke and cerebral edema in the event of neurological deterioration.