Hepatic encephalopathy is an uncommon cause of neurologic deterioration associated with hyperammonemia, which results from hepatic dysfunction or altered ammonia metabolism. Often overlooked, hyperammonemia may occur via any of several pathophysiological processes, and in the setting of malignancy, it is a potentially reversible cause of confusion and coma. Hepatic dysfunction as a result of malignant infiltration, chemotherapeutic toxicities, targeted anticancer therapies, reactivation hepatitis, portosystemic shunting, and transarterial chemoembolization (TACE) is discussed, and an approach to etiological diagnosis and management is outlined.