Background: Overweight and obesity are growing public health concerns worldwide. Bariatric surgery is a modality of weight reduction; however, postoperative pain can increase the length of hospital stay, with all the associated consequences. While regional anesthesia is an available option, the feasibility of performing abdominal wall blocks on patients with obesity is questionable. Methods: Sixty adult patients with a body mass index of 40–50 kg/m2 undergoing laparoscopic bariatric surgery were randomly assigned to receive either an ultrasound-guided transversus abdominis plane (TAP) or erector spinae plane (ESP) block. The primary outcome was the analgesic effect in the first 24 h postoperatively, assessed using the mean visual analog scale (VAS) score. Secondary outcomes were the time required for a successful block, incidence of complications, time to first rescue analgesia, time to flatus or stool passage, and total opioid consumption. Results: The mean VAS score during the first 24 h was higher with the TAP block than with the ESP block (2.78 ± 0.34 vs. 2.32 ± 0.12, P < 0.001). Additionally, the time to first rescue analgesia was greater with the ESP block (P = 0.001) and the time required for a successful block was higher with the TAP block (P = 0.001). However, the incidence of complications, total opioid consumption, and other secondary outcomes was similar between the groups. Conclusions Compared with the TAP block, the bilateral ESP block is a more feasible and effective method for intra- and postoperative analgesia in patients undergoing laparoscopic bariatric surgery.