Background: Ultrasound-guided bilateral transversus abdominis plane (TAP) block provides analgesia by blocking the anterior abdominal wall afferent nerves. We evaluated the analgesic efficacy of TAP block as a component of multimodal analgesia in patients undergoing major abdominal oncosurgeries. The study design is prospective, randomized, and controlled. Materials and methods: Sixty patients of 18–65 years of age of either sex and American Society of Anesthesiology (ASA) grade I, II, or III undergoing major abdominal oncosurgeries were randomized to the TAP group (n = 30) and the control group (n = 30). All patients received standard general anesthesia. In the TAP group patients after the completion of the surgery, ultrasound-guided 18G Braun Perifix epidural catheter was placed in TAP and 50 mg bupivacaine was given bilaterally 8 hourly up to 24 hours. In the control group patients, the TAP block was not performed. Patients of both groups received patient-controlled analgesia (PCA) with intravenous morphine and IV paracetamol 1 g 8 hourly. In the postoperative anesthesia care unit (PACU), we observed all patients visual analogue scale (VAS) pain score at rest and on knee flexion, PCA morphine demands, sedation score, and nausea/vomiting score at 0, 2, 4, 6, 12, 18, and 24 hours. The primary outcome measure was to study the VAS pain score in TAP and control group patients at rest and on knee flexion up to 24 hours. The secondary outcome measure was to calculate the PCA morphine requirement in both groups with 24 hours’ time frame. Results: Patients receiving TAP block with 0.25 % bupivacaine 20 mL eight hourly had reduced postoperative VAS pain score at rest and on knee flexion compared to the control group (p < 0.05). Up to 24 hours in PACU, IV morphine requirement in the TAP group was reduced to 19 mg as compared to 32 mg in the control group which is highly significant (p < 0.001). Conclusion: Patients receiving TAP block had effective postoperative analgesia and decreased morphine requirement up to 24 hours; hence, TAP block should be considered as a major component of multimodal analgesia for pain management of major abdominal oncosurgeries. The study has been registered with www.clinicaltrials.gov ID NCT03165383.