Introduction A patient with chronic lithium toxicity developed a life-threatening ventricular arrhythmia that resolved during removal of lithium by hemodialysis. Chronic lithium toxicity commonly results from diminished elimination and can produce neurotoxicity. Cardiovascular complications have been reported and generally affect the sinoatrial node and produce bradyarrhythmias. The majority of these arrhythmias require no emergent intervention. Ventricular arrhythmias associated with lithium toxicity are occasionally mentioned in the literature, but actual cases are rarely reported. Case Report A 74-year-old man was brought into the emergency department with a 3-day history of progressive encephalopathy, tremor, and weakness. The lithium level was elevated at 2.2 mmol/L, with a normal serum potassium. Electrocardiography revealed nonsustained monomorphic ventricular tachycardia (120-130 beats/min) lasting up to 1 min, alternating with sinus bradycardia and wandering atrial pacemaker. Episodes of monomorphic ventricular tachycardia recurred >100 times. The patient required a norepinephrine infusion for hypotension. Emergent hemodialysis was initiated to remove lithium and to treat the monomorphic ventricular tachycardia, which was felt to be secondary to lithium toxicity. Episodes of monomorphic ventricular tachycardia abated as hemodialysis progressed. The episodes resolved completely within 4 h of initiating hemodialysis. The patient was discharged home in sinus rhythm on day 5. Lithium was not reinstated. Conclusion Monomorphic ventricular tachycardia associated with chronic lithium toxicity is exceptionally rare. Hemodialysis is a treatment option.