In species with non-invasive implantation by conceptus trophectoderm, fetal/maternal communications occur across the endometrial epithelia. The present studies identified changes in junctional complexes in the ovine endometrium that regulate paracellular trafficking of water, ions and other molecules, and the secretory capacity of the uterine epithelia. Distinct temporal and spatial alterations in occludin (OCLN), tight junction protein 2 (TJP2), and claudin (CLDN) 1-4 proteins were observed in the endometrium of cyclic and early pregnant ewes. Dynamic changes in tight junction formation were characterized by an abundance of tight junction proteins on d 10 of the estrous cycle and pregnancy that substantially decreased by d 12. Early progesterone administration advanced conceptus development on d 9 and d 12 which was associated with loss of tight junction associated proteins. Pregnancy increased tight junction associated proteins between d 14 and 16. Cadherin 1 (CDH1) and beta-catenin (CTNNB1), which form adherens junctions, were abundant in the endometrial glands, but decreased after d 10 of pregnancy in the luminal epithelium and then increased by d 16 with the onset of implantation. Results support the ideas that progesterone elicits transient decreases in tight and adherens junctions in the endometrial luminal epithelium between d 10 and 12 that increases selective serum and tissue fluid transudation to enhance blastocyst elongation, which is subsequently followed by an increase in tight and adherens junctions between d 14 and 16 that may be required for attachment and adherence of the trophectoderm for implantation. The continuous presence of tight and adherens junctions in the uterine glands would allow for vectorial secretion of trophic substances required for conceptus elongation and survival.