Primary brain tumours and brain metastases often have a poor prognosis and newly available immunotherapies have, for the most part, shown limited efficacy in these tumour types. As such, there is a real need to understand the factors that shape the immune microenvironment in brain tumours. Reporting in Cell, Maas et al. show that neutrophils in human and mouse brain tumours show a more immune-suppressive and proangiogenic phenotype and they identify soluble factors in the brain tumour microenvironment (TME) that contribute to this.