Successful of embryo implantation requires synchronization between maternal and fetal factors to promote endometrial receptivity. In this scenario, the maternal immune system may play an important role in the establishment as well in the development of conceptus until onset of parturition in eutherian mammals. Our study aimed to identify and quantify the subpopulations of immune cells in the bovine pregnant endometrium. We hypothesized that the endometrial immune cells pool change as pregnancy progresses. Samples from early (33 ± 1.5 d), mid (170 ± 16.9 d) and late pregnancy (227 ± 10.8 d) were obtained from a local abattoir (n = 5, per group). Cryostat sections were labeled for CD4 (T helper), CD8 (T cytotoxic), CD14 (macrophage), CD25 (activation T cells) and WC1 (γδ). The samples were analyzed under epifluorescence microscope. The number of positive cells was counted and normalized to the total number of cells per mm² in 5 random fields for each group/marker. Data were analyzed separately for each marker by least square ANOVA using the GLM procedure of SAS. The WC1⁺ cells were most prominent in the endometrial stroma, with greater cell number in mid than in early and late stages of pregnancy (P < 0.01). Moreover, CD4⁺ (P = 0.09) and CD8⁺ (P < 0.01) decreased in number in late pregnancy, whereas CD25⁺ cells were low only in mid-pregnancy (P = 0.02). CD14⁺ cells increased, respectively, 3- and 4-fold in mid and late stages of pregnancy (P < 0.01). Our results show that there is a deviation of endometrial immune cells subpopulations during pregnancy in the cow. In early pregnancy, there is a predominance of immune cells involved in regulation of immune response (CD3, CD4 and CD8) to allow embryo attachment and survival; whereas in mid-pregnancy, number of cells with trophic function are increased (CD14 and WC1) likely to allow placental development. In late pregnancy, there is a recruitment of cells involved in inflammatory response to induce placental detachment and parturition (CD14 and CD25).