Persistent mating-induced endometritis (PMIE) is a significant cause of mare infertility hence its treatment would advance the management of susceptible mares. Preimplantation factor (PIF) is secreted by viable embryos, including human, mouse and cattle, and is essential for maternal immune-tolerance without immune-suppression by modulating inflammation. This preliminary study aimed to test whether PIF exerts inflammatory-modulating properties upon equine endometrium challenged with Escherichia coli-derived lipopolysaccharide (LPS) using endometrial explant culture. Follicular (n = 3), luteal (n = 4), anoestrous (n = 4) and transitional (n = 4) stage endometrial explants were established and cultured in triplicate in either serum-free medium alone (control) or medium with; 50 or 100 nmol/L synthetic PIF (sPIF); 3 μg/mL LPS; LPS and 50 or 100 nmol/L sPIF; or scrambled PIF (PIFscr; same amino acid composition arranged in a different order). Media samples were collected at 24 and 72 h, representing acute and chronic inflammatory response. Radioimmunoassay determined Prostaglandin F2α (PGF2α) as an inflammatory marker. The only significant observation was the abrogation of PGF2α response to LPS challenge by 100 nmol/L PIF for follicular stage tissue, 24 h after treatment. Further studies are therefore, warranted to realise PIF potential in managing PMIE.