The number of people receiving systemic anti-cancer treatment and presenting at emergency departments with treatment-related problems is rising. Nurses will be the first point of contact for most patients and need to be able to recognise oncological emergencies to initiate urgent assessment of patients and referral to the acute oncology team so that the most appropriate care can be delivered promptly. This article discusses the role of acute oncology services, and provides an overview of the most common acute oncological emergencies.