Abstract: The aim of this study was to find out whether the administration of piroxicam prior to embryo transfer might improve implantation and pregnancy rates in patients under IVF therapy. This study was designed as a prospective randomized clinical trial. In total, 180 fresh IVF-ET cycles were randomly divided into treatment and control groups. The treatment group (90 cycles) received an oral dose of 10 mg of piroxicam and the control group (90 cycles) received a placebo, 1-2 h before ET. The woman`s age, duration and etiology of infertility, number of oocytes retrieved, number of embryos transferred and the score of embryo transferred showed no significant differences in both groups. The implantation rate and clinical pregnancy rate were significantly higher in the piroxicam treatment group compared with the control group. The implantation rate was 12.3 vs. 7.7% (p-value = 0.04) and the clinical pregnancy rate was 25.5 vs. 10% (p-value = 0.015) in the piroxicam vs. control groups, respectively. The number of miscarriage was one in the piroxicam group and five in the control group (p-value = 0.01). In addition, there were two twins pregnancies in piroxicam group and one in control group. This result proposes that the treatment with piroxicam before ET could prepare a suitable uterus for embryo implantation.