Lidocaine has been shown to be clinically beneficial during bariatric surgery. However, information about lidocaine serum concentrations in this setting is scarce. This prospective clinical trial included 42 obese patients undergoing laparoscopic bariatric surgery. They received lidocaine based on adjusted body weight. Administration began with a 1.5 mg·kg−1 bolus of intravenous lidocaine followed by a continuous infusion of 2 mg·kg−1·hour−1. After skin closure, administration was decreased to 1 mg·kg−1·hour−1 until discharge from the recovery room. No serum concentrations of lidocaine were outside the usual accepted range (1.5–5 µg·mL−1).