Background: Endometrial thickness (ET) is one of the best predictors of implantation rate and continued success rate for pregnancy. There were possible beneficial effects of sildenafil citrate or estradiol on endometrial receptivity. The aim of this study was to compare the effect of Vaginal Sildenafil versus Oral Estradiol Valerate on Endometrial Thickness and Pregnancy Rate in infertile women undergoing induction of ovulation by clomiphen citrate. Patients and Methods: This Randomized control study was conducted on 44 infertile women undergoing induction by Clomiphen Citrate attending infertility and U/S unit, Obstetrics & Gynecology Department, Zagazig University Hospital, during the period from December 2018 to August 2019. Patients were randomized into 2 groups (22 in each group); group (1) received Sildenafil and group (2) received oral Estradiol Valerate. Results: The results of present study showed that there was no statistically significant difference between the studied groups regarding age, Type of infertility, body mass index (BMI), follicle stimulating hormone (FSH), luteinizing hormone (LH), Thyroid stimulating hormone (TSH), prolactin, ovulation rate, follicles number and size, results of pregnancy test and fetal pulse detection between studied group. But there was a statistically significant difference between them in endometrial thickness on the day of triggering. Conclusion: It could be concluded from this study that vaginal use of vaginal sildenafil citrate 20 mg or oral Ethinyl Estradiol in infertile females increase endometrial thickness and support embryo growth but Ethinyl Estradiol has better results on endometrial thickness than sildenafil. But both treatments have the same effect on pregnancy rate.