Eosinophilia is frequently observed in cancer and eosinophils are attracted to tumours but it is still unknown whether they play an active part in tumour rejection. Carretero et al. have shown that, in the presence of tumour-specific CD8+ T cells, eosinophils secreted chemokines that guided T cells to melanoma tumours grown in C57BL/6N mice, which resulted in tumour eradication and survival. Conversely, depletion of eosinophils resulted in impaired infiltration of T cells into the tumour. Activation of eosinophils also triggered substantial changes in the tumour microenvironment, including macrophage polarization and normalization of the tumour vasculature, which facilitates T cell infiltration and tumour rejection.