The chronic degenerative endometritis (CDE) is recognised as directly related to age and infertility in the mare. In this study, the 14 days post ovulation (PO) pregnancy rate was assessed in 60 barren mares affected by CDE, submitted to platelet-rich-plasma intrauterine infusion (PRPI) 24 hours PO. Data showed a significant positive effect of PRPI on the chance to become pregnant in mares affected by Kenney I-II CDE. The overall 14 days PO pregnancy rate was 75%. Sixty-nine % of the overall pregnancies was achieved with the 1st PRPI, but an additional 31% was obtained with the 2nd PRPI at the subsequent heat, increasing significantly the number of pregnancies. Although the 1st PRPI lead to a higher pregnancy rate than the 2nd PRPI (52 vs 23%), the repetition of the treatment had a significant positive effect on the overall pregnancies. Mare’s young age positively influenced the chance to become pregnant and was associated to endometritis Kenney I. Mares with endometritis Kenney I had better chance to become pregnant than those with endometritis Kenney II. The PRPI proved, therefore, to be beneficial in barren mares with CDE, and resulted in high overall pregnancy rate achievement in barren mares.