Hyponatremia is frequently seen in heart failure patients and has a high mortality rate. If not treated adequately, acute and chronic hyponatremia may worsen the prognosis of heart failure. Despite its high incidence in heart failure patients, other underlying conditions that possibly lead to the incidence of hyponatremia may be underestimated, thus making its treatment more difficult. In this case study, we describe a rare case of levetiracem-induced and tolvaptan-resistant hyponatremia.