The studies posits that there is not sufficient evidence to support the use of intrauterine platelet-rich plasma (PRP) infusion in patients with recurrent implantation failure (RIF). This study aims to investigate the effects of infusion of PRP on patients with unexplained-RIF in fresh and frozen embryo transfer (ET) cycles. A total of 80 participants were included in this study. The participants were randomly assigned to one of two groups with and without PRP infusion. Each of the PRP and control groups were also divided into fresh and frozen ET subgroups. ET outcomes were compared between groups. Clinical pregnancy rate was significantly higher in Frozen ET in PRP group than other subgroups (p < 0.0001). Miscarriage rate were significantly lower in PRP group than control group. Pregnancy complications and preterm labor were significantly higher in PRP group than control group (p < 0.0001). Live birth and healthy baby rate were significantly higher in PRP group than control group (p < 0.0001). The intrauterine infusion of 0.8-1 ml of PRP 48 h before blastocyst ET at fresh and frozen cycles can be an efficient treatment option for u-RIF patients. Also, results indicated that the clinical pregnancy rate was equal to the live birth rate at fresh ET cycles, whereas the live birth rate was lower than the clinical pregnancy rate at frozen ET cycles. Therefore, considering the superiority of fresh cycles over freeze cycles, the infusion of PRP into the uterus of patients with RIF is recommended to be done at fresh ET cycles.Trial registration: NCT, NCT03996837. Registered 25/06/2019. Retrospectively registered, http://www.clinicaltrial.gov/ NCT03996837.