Aim:To compare the effect of ultrasound-guided modified thoracolumbar interfascial plane (TLIP) block versus local anesthetic infiltration on the wound site for post-op analgesia in patients undergoing lumbar disk surgery with spinal anesthesia.Material and Methods:This prospective and observationally planned study included 42 patients from the ages of 18 to 75 years, American Society of Anesthesiologists classes I–III, who underwent lumbar disk surgery. In Group L, bupivacaine infiltration was performed on the surgical incision line. In Group T, TLIP block was performed with ultrasound. In the postoperative period, Visual Analogue Scale (VAS) values were also investigated and recorded on the 10th day after discharge. Nausea, vomiting, and sedation score values and analgesic doses used by all patients in the postoperative period were recorded.Results:During any of the postoperative follow-up hours, the VAS score was ≤ 3 (mild pain), and those who did not need tramadol were 80.9% (n = 17) in Group T and 71.4% (n = 15) in Group L. VAS scores at the 1st, 4th, and 8th hours were statistically lower in Group L than those in Group T (p values: 0.011, 0.028, and 0.029). The average amounts of tramadol consumption per patient were determined as 19.04 mg ± 40.23 in Group T and 27.38 ± 44.65 mg in Group L in the first 24 hours postoperatively. There was no statistically significant difference between groups (p = 0.519).Conclusion:In our study, we determined that the modified In this study, it was determined that the modified TLIP block application performed for the purpose of post-op analgesia in lumbar disk surgery was not superior to local anesthetic infiltration in terms of postoperative opioid consumption and VAS scores.