Migration of functional neutrophils into the uterus following parturition is thought to be key to uterine health and fertility in early lactation dairy cattle, but the activity of uterine neutrophils has rarely been investigated. Data from 2 studies on peripartum dairy cows were used to assess relationships between measures of immune function and uterine granulocyte oxidative burst. Whole blood from multiparous Holstein cows (n = 39) on d 10 and 38 relative to calving was collected for flow cytometry and complete blood count analysis. On the same days, endometrial samples were collected by cytobrush technique. Cytobrushes were rolled onto a slide which was stained for polymorphonuclear cells (PMN; 300 cells counted) and then immersed in culture media. Whole blood and uterine brush samples were prepared for flow cytometry to measure oxidative burst of granulocytes after phorbol myristate acetate stimulation. Labeled antibodies (CH138a and CD45) and dihydrorhodamine were used to identify granulocytes and quantify oxidative burst, respectively. Granulocyte response (GR) was calculated as stimulated – basal oxidative burst. Statistical models evaluated associations with predictors, their interactions with day, and the random effect of study. Outliers were identified and removed using conditional residuals. Uterine GR was not associated with blood GR on d 10 (P = 0.60) but was positively associated with blood GR on d 38 (r² = 0.41, P = 0.05). Similarly, on d 38, blood leukocytes/μL (r² = 0.51, P = 0.01) and even band neutrophils/μL (r² = 0.67, P = 0.03) were positively associated with uterine GR, though not on d 10. Regardless of time point, the proportion of PMN in cytobrush samples was positively associated with uterine GR (r² = 0.55, P < 0.001). Blood markers of immune status predicted uterine GR only after the transition period, but greater uterine PMN populations are predictive of greater oxidative burst potential of uterine granulocytes across time points.