With the increase in utilization of alternative medications to manage cancer treatment-related side effects, pharmacovigilance of alternative drug therapies, specifically herbal supplements, has become of increasing importance in the oncologic setting. This chapter focuses on the pharmacovigilance of herbal supplements in the setting of cancer drug therapy and explores national and international drug policies that have been employed to mitigate adverse herbal supplement events (AHEs). This chapter examines common drug-herbal supplement interactions, discusses the mechanisms behind these interactions, and investigates several common pharmacovigilance reporting methods clinicians can use to report adverse events. This chapter will also describe policies and strategies that can be employed to monitor use of these alternative drug therapies, and examines global harmonization efforts to reduce AHEs in the cancer setting. The safety of herbal medicines has emerged as an international public health priority, and we explore how oncology providers may directly apply the knowledge garnered herein to help guide their clinical management of oncology patients utilizing alternative medications.