The equine conceptus presents an extensive mobile stage from days 9 to 16 after ovulation, during which it becomes fixed to one of the uterine horns. Throughout mobility, the conceptus secretes fibrinogen (an integrin-binding ECM). We hypothesized that conceptus-derived fibrinogen is converted into fibrin and aids in fixation via integrin receptors. We determined that RGD-binding integrins are expressed in endometrial and embryonic/fetal cells and interact with fibrinogen. Moreover, endometrial and embryonic cells presented the machinery to convert fibrinogen into fibrin and maintain the fibrin network. Overall, we demonstrated that conceptus-derived fibrinogen is likely converted to fibrin at the embryo-maternal interface and mediates cell adhesion via RGD-binding integrins.