Introduction: Endometrial thickness is a key prognostic factor for embryo implantation in assisted reproductive technology (ART) cycles. Materials and Methods: This prospective observational study evaluated the effectiveness of intrauterine platelet-rich plasma (PRP) infusion in patients with refractory thin endometrium (RTE) unresponsive to conventional hormonal therapy. Thirteen consecutive patients were included. Autologous PRP was obtained after centrifugation, and two intrauterine infusions of 1 mL were administered 48 hours apart. Results: Mean endometrial thickness increased from 4.8 mm to 7.2 mm following PRP treatment. The clinical pregnancy rate was 84.6%. Conclusion: Intrauterine PRP infusion appears to be an effective and safe therapeutic option for improving endometrial thickness and clinical pregnancy rates in patients with refractory thin endometrium.