Scribble (Scrib) is a scaffold protein with multifunctional roles in PCP, tight junction and Hippo signaling. This study shows that Scrib is expressed in stromal cells around the implantation chamber following implantation. Stromal cells transform into epithelial-like cells to form the avascular primary decidual zone (PDZ) around the implantation chamber (crypt). The PDZ creates a permeability barrier around the crypt restricting immune cells and harmful agents from maternal circulation to protect embryonic health. The mechanism underlying PDZ formation is not yet known. We found that uterine deletion of Scrib by a Pgr-Cre driver leads to defective PDZ formation and implantation chamber (crypt) formation, compromising pregnancy success. Interestingly, epithelial-specific Scrib deletion by a lactoferrin-Cre (Ltf-Cre) driver does not adversely affect PDZ formation and pregnancy success. These findings provide evidence for a previously unknown function of stromal Scrib in PDZ formation, potentially involving ZO-1 and Hippo signaling.