The transversus abdominis plane (TAP) block acts on the nerves localised in the anterior abdominal wall muscles. We evaluated the efficacy on post-bariatric (PB) patients undergoing body-contouring abdominoplasty. We retrospectively evaluated PB patients undergoing abdominoplasty with flank liposuction and compared results to a matched group of TAP aesthetic patients. Outcomes evaluated were the analgesic requirements during the early postoperative days. Fifty-one patients (PB n = 27, aesthetic n = 24) were assessed. No complications were observed. All PB patients required analgesia until the second postoperative day contrarily to most aesthetic ones. Patients with greater flap resected and higher pre-abdominoplasty BMI had greater morphine consumptions. In PB patients, the larger amount of tissues resected corresponded to a greater stimulation of pain fibres that cannot be paralleled by a concomitant increase of the local anesthetic administered. This partially invalidates TAP's efficacy on PB patients.