Although arteriovenous malformations (AVMs) are typically benign lesions, massive ones can lead to severe complications, including heart failure. Notably, there is no standardized treatment for AVMs. Moreover, management of AVMs can be challenging when these lesions involve vital organ systems, such as the head and neck. In this report, we describe embolization of a massive cervical AVM in a pediatric patient with heart failure. A 10-year-old boy presented with severe heart failure secondary to a massive AVM in the neck (right side). Despite 3 unsuccessful arterial embolization procedures, venous embolization of the dominant outflow vein using a coil and n-butyl-2-cyanoacrylate, lipiodol, and ethanol proved effective, and symptoms, cerebral natriuretic peptide level (568-29 pg/mL), and echocardiography were significantly improved. Although residual AVM persisted in the right upper extremity for 6 months after surgery, his cardiac function remained preserved, and his activities of daily living have improved. Venous embolization is a valuable treatment modality for type II AVMs with a dominant outflow vein. However, considering the patient burden associated with large AVMs, multiple therapeutic interventions at appropriate intervals and long-term follow-up are important. We present a pediatric patient with a type II massive arteriovenous malformation (AVM) in the neck and severe heart failure. Despite undergoing 3 arterial embolization procedures, his condition remained unchanged. However, venous embolization of the dominant outflow vein resulted in a significant improvement in symptoms. This case emphasizes the importance of considering multiple and appropriately timed therapeutic interventions, particularly for massive AVMs, to optimize patient outcomes while minimizing treatment burden.