Wernicke encephalopathy is a well-described neurological complication of thiamine deficiency that is classically characterized by a triad of mental confusion, ophthalmoplegia, and gait ataxia. Although most commonly linked to alcoholism and thiamine deficiency in adults, it can present in pediatric patients. Wernicke encephalopathy presenting as dysnatremias is not well described. This report describes a developmentally delayed 21-month-old male with restrictive dietary habits who eventually developed focal neurological deficits. He was found to be hyponatremic consistent with syndrome of inappropriate antidiuretic hormone (SIADH). Additionally, he had brain magnetic resonance imaging findings consistent with Wernicke encephalopathy. He improved with thiamine administration and correction of his hyponatremia. His case highlights the importance of broadening the differential for altered mental status in the setting of SIADH. Similarly, his case provides an example for why primary care pediatricians should remain vigilant in caring for patients with developmental delay and restricted diets, as even rare complications are possible.