Background: repeated implantation failure (RIF) is a major challenge in reproductive medicine. Platelet rich plasma (PRP) was able to promote the endometrial growth and improve pregnancy outcome of patients with thin endometrium. Aim of the study: it was to evaluate the effectiveness of intrauterine infusion of PRP in treatment of thin endometrium in frozen-thawed embryo (FTE) transfer. Patients and Methods: the study included 10 infertile patients with thin endometrium (<7mm) in Frozen Embryo Transfer (FET) program. Estradiol valerate 12 mg/d was started on day 3 of menstrual cycle. PRP was prepared from autologous blood and infused into the uterine cavity. Endometrial thickness was re-assessed and if the endometrial thickness wasn't satisfactory infusion of PRP was repeated 2-4 times. Cleavage stage embryos were transferred on the 3 rd day after progesterone administration, and blastocysts were transferred on the 5th day after progesterone administration. Results: the endometrial thickness increased after PRP infusion in all the patients, and reached >7mm on the day of progesterone administration. Sixty percent of the patients became pregnant; 83.3% continued pregnancy and 16.7% experienced missed abortion. Conclusion: intrauterine PRP may be effective in promoting endometrial growth, endometrial thickness, and improving pregnancy out come in repeated implantation failure.