Mucositis is a common and feared complication of anticancer therapy that can affect up to 90% of certain populations of patients with cancer. Even seemingly uncomplicated mucositis, which is often self-limited, can result in intense patient discomfort and decline in quality of life. Severe mucositis can be complicated by uncontrolled pain, superinfection or systemic infection, bleeding, and dehydration, and severe mucositis can lead to interruptions or de-escalation in anticancer treatment, resulting in worse oncologic outcomes. This article provides an evidence-based summary to guide practicing oncologists in the assessment, prevention, and management of mucositis induced by chemotherapy, radiotherapy, and targeted therapy.