This online resource provides supplementary items used to analyze data in the work, "Single-cell RNA sequencing characterization of Holstein cattle blood and milk immune cells during a chronic Staphylococcus aureus mastitis infection", by Wiarda et al. Cells were collected from milk and blood of three cattle with chronic mastitis infections caused by experimental Staphylococcus aureus challenge. Isolated cells were processed for single-cell RNA sequencing, resulting in a dataset of 35,338 cells distributed across 62 cells clusters. Cell clusters were classified as granulocytes, monocyte/macrophage/conventional dendritic cells, B cells/antibody-secreting cells, T cells/innate lymphoid cells, plasmacytoid dendritic cells, and non-immune cells. A data subset consisting of 30 granulocyte clusters was also created. Data objects of total cell and granulocyte datasets are included here (.h5seurat files), as well as results of pairwise differential gene expression of all cell clusters (resulting in over 4.3 million differentially expressed genes), and a data object containing cell neighborhoods used for differential abundance testing.