Imatinib, a tyrosine kinase inhibitor, primarily used to treat chronic myeloid leukemia, has shown a survival benefit in gastrointestinal stromal tumors (GISTs). The most common toxicities of imatinib include fluid retention, diarrhea, nausea, fatigue, muscle cramps, abdominal pain, and rash. Imatinib-related cardiotoxicity is a rare condition, and its clinical severity varies between asymptomatic mild ventricular dysfunction and severe congestive heart failure (CHF). We report the case of a 64-year-old woman with a history of GIST who presented to our clinic with rapidly progressive dyspnea. After 8 weeks of imatinib treatment, the patient developed CHF. Echocardiography showed decreased ejection fraction. Imatinib was stopped and diuretic therapy was started. Two weeks later, she died. Cardiac shock was her cause of death.