While Wilms tumors are the most frequently detected renal cancer type in children, extrarenal Wilms tumors (ERWTs) remain rare. This report is the first to describe hypertension and dilated cardiomyopathy in a patient with an ERWT. A six-month-old male infant presented with an abdominal mass and paroxysmal hypertension, echocardiography revealed dilated cardiomyopathy with an ejection fraction of 34%, as well as substantially increased plasma renin activity. Pathology yielded a definitive diagnosis of ERWT. Cardiac function and blood pressure gradually returned to normal after tumorectomy. The early diagnosis of such a tumor together with efficient oncologic treatment are vital to optimal patient outcomes.