The tumour microenvironment is composed of numerous cell types, including tumour cells, immune cells and stromal cells. The cancer cells interact with the tumour microenvironment to suppress anticancer immunity. In this study, we molecularly dissected the tumour microenvironment in breast cancers by single cell RNA-seq. We profiled the landscape of the tumour microenvironment in breast cancer by analysing the single cell transcriptomes of 52,163 cells from the tumour tissues of 15 breast cancer patients. Tumour cells and immune cells were analysed simultaneously in individual patients at single cell level. This study explores the diversity of the cell types in the tumour microenvironment and provides information on the mechanisms of escape from clearance by immune cells in breast cancer.