Although chemotherapy is a well established treatment modality, chemotherapy errors represent a potentially serious risk of patient harm. We reviewed published research from 1980 to 2017 to understand the extent and nature of medication errors in cancer chemotherapy, and to identify effective interventions to help prevent mistakes. Chemotherapy errors occur at a rate of about one to four per 1000 orders, affect at least 1–3% of adult and paediatric oncology patients, and occur at all stages of the medication use process. Oral chemotherapy use is a particular area of growing risk. Our knowledge of chemotherapy errors is drawn primarily from single-institution studies at university hospitals and referral centres, with a particular focus on prescription orders and pharmacy practices. Although the heterogeneity of research methods and measures used in these studies limits our understanding of this issue, the rate of chemotherapy error-related injuries is generally lower than those seen in comparable studies of general medical patients. Although many interventions show promise in reducing chemotherapy errors, most have little empirical support. Additional research is needed to understand and to mitigate the risk of chemotherapy medication errors.