Background: Postoperative pain associated with total knee replacement surgery (TKR) is considerable and requires adequate analgesia. Objectives: To study the additive effect of femoral nerve block (FNB) and 0.2 mg intrathecal morphine (ITM) compared with either technique alone for postoperative analgesia in patients undergoing (TKR) under spinal anesthesia. Design: Prospective double-blind randomized comparative study. Setting: University hospital. Methods: Sixty ASA I–III subjects undergoing unilateral TKR were enrolled in a randomized, parallel group, double-blind study receiving 15 mg hyperbaric bupivacine spinal anesthesia plus 0.2 mg ITM (Group M), FNB (Group F), or 0.2 mg ITM and FNB (Group MF) for postoperative analgesia. Assessment parameters included; postoperative morphine PCA consumption in first 48 h postoperative, time to first request for rescue analgesia, pain scores, length of hospital stay and adverse effects. Results: The time to the first administration of rescue intravenous morphine PCA, was longer in the MF group (8.21 ± 0.85 h) compared with the M (6.31 ± 1.45 h, P0.001) and F (4.99 ± 1.0 h, P0.001) groups. Morphine consumption was lower in MF group [6.3 ± 0.47 (6-7) mg] vs. [11.2 ± 1.32 (9-14) mg] and [13.75 ± 0.72 (13-15) mg] in M and F groups, respectively (P0.001). From the fourth till the 48th h postoperatively, VAS scores were significantly decreased in the FM group compared with M and F groups (p0.001). There were no recorded differences among groups in the length of hospital stay or postoperative adverse effects. Limitations: This study is limited by its small sample size. Conclusion: The combination of 0.2 mg ITM and single-shot FNB provided superior postoperative analgesia after TKR compared with either technique alone.