The past decade has seen significant advancement in the locoregional management of liver tumors; novel and promising therapies such as transarterial chemoembolization, radioembolization, and radiofrequency ablation are now available. The development of new techniques and devices has led to the improved safety and efficacy profiles of external-beam radiation. Radioembolization with yttrium-90 ((90)Y) microspheres has emerged as a safe and efficacious treatment modality for liver malignancies. The purpose of this article is to present a comprehensive evidence-based review of the complications and adverse events that may be associated with radioembolization with (90)Y microspheres. Strategies to mitigate these adverse events are also discussed.