<p>Nesfatin-1 is a peptide hormone that is commonly associated with appetite regulation and is primarily expressed in the brain. However, it has recently been identified in various peripheral organs, including the ovaries and uterus. This study aimed to investigate the expression and functional role of nesfatin-1 in the mouse endometrium. Due to the lack of established mouse endometrial cell lines, a primary culture system was developed by isolating endometrial cells through enzymatic digestion, enabling in vitro analyses. We examined the presence and regulatory potential of nesfatin-1 in these cells, focusing particularly on endometrial decidualization, a critical process for implantation and pregnancy maintenance. Our results revealed that nesfatin-1 and its binding sites are expressed in mouse endometrial cells. Furthermore, Nucb2 mRNA expression was significantly increased following estradiol treatment but not progesterone treatment, suggesting hormone-specific regulation of nesfatin-1 expression. Notably, nesfatin-1 treatment to mouse endometrial cells resulted in a significant upregulation of decidualization-associated genes, including prolactin family 8, subfamily a, member 2 (Prl8a2), alkaline phosphatase (Alpl), and bone morphogenetic protein 2 (Bmp2). Furthermore, in a delayed implantation mice model, there was a significant decrease in Nucb2/nesfatin-1 expression and decidualization-associated genes. Importantly, nesfatin-1 administration restored the expression of these genes in the delayed implantation conditions. Taken together, these findings demonstrate that nesfatin-1 plays a pivotal role in promoting endometrial decidualization and successful implantation, suggesting its potential as a therapeutic target for enhancing fertility and improving pregnancy outcomes.</p>