Objectives: To explore the efficacy of intrauterine infusion of autologous platelet-rich plasma (PRP) in infertile ladies as an adjuvant to clomiphene citrate (CC) in ladies with previous CC failure attributed to a thin endometrium (≤ 7 mm). Design: A pilot prospective self-controlled trial. Patients and methods: The study included thirty anovulatory PCOS women with CC failure for 3 cycles with a thin endometrium (7 mm). All patients underwent ovarian stimulations for 2 cycles; 1) Control cycle: 30 women received CC alone and one got pregnant and 2) Study cycle;29 women received CC plus an intrauterine infusion of PRP. Main endpoints included the comparison of the endometrial thickness (ET) and endometrial vascularity pattern by power Doppler on the day of hCG injection between both treatment cycles. Results: There was a statistically significant increase in the endometrial thickness on the day of hCG injection with CC plus PRP compared to CC alone (8.98 ±1.31 vs, 5.8 ±1.2; p < 0.0001). There was a significant improvement in the endometrial blood flow with the use of PRP (p= 0.00004). The pregnancy rate is significantly higher in the PRP cycles compared to control cycles (7 pregnancies (24.14%) vs. one pregnancy (3.3%) respectively; p = 0.0257) Conclusion: Intrauterine infusion PRP seems to be a promising adjuvant to increase endometrial thickness and endometrial blood flow with subsequent improvement in clinical pregnancy rate in ladies with CC failure due to thin endometrium