Background: In major operations, like femoral bone surgery due to extension of surgical field, we may have severe bleeding and massive transfusion. In this study, we aimed to evaluate the effect of tranexemic acid on reduction of bleeding and transfusion in femoral shaft surgery. Methods: After obtaining consent, 80 candidates of femoral shaft surgery aged 18-64 years, in score 1 and 2 of The American Society of Anesthesiologists scale (ASA) were entered a double blind prospective clinical trial. Patients randomly divided into 2 groups of receiving 15 mg/kg tranexemic acid in 5 ml solution and receiving 5 ml normal salin as placebo. All patients received standard monitoring and spinal anesthesia was done by injecting bupivacaine. The amount of bleeding was measured and recorded. Findings: There was no significant difference between the two groups in age and sex. Mean blood loss and transfusion requirement in tranexemic acid group was significantly less than the placebo group (P < 0.05). There was no significant difference between the two groups in nausea, vomiting and vertigo. Conclusion: Our results indicated that 15 mg/kg intravenous tranexemic acid (one hour before the operation) was significantly effective in decreasing blood loss and transfusion requirement.