Care for cancer patients is very complex with many treatments involving drugs that can be toxic outside of the therapeutic range. As such, cancer patients are a particularly vulnerable population within the healthcare system, with any error potentially being harmful to a population whose health is already compromised. Self-reported patient safety events can provide a window into healthcare, revealing areas of care that require improvement. We identified events occurring in oncology units that both caused harm and were involved cancer patients for both out-patients and in-patients. Across all events, adverse drug reactions and intravenous-related events were the most common. Other relatively frequent events included those related to poor care coordination and falling. These results illustrate the safety risks patients’ face when being treated with cytotoxic drugs and offer insight to areas in which patient care can be improved.