Morbid obesity is associated with excessive daytime sleepiness and reduced health-related quality of life. We prospectively evaluated the pre- and postoperative responses of bariatric surgery recipients with the Epworth Sleepiness Scale (ESS) and the Short Form-12. Participants (n = 223; 79% women) with a mean body mass index (BMI) and ESS of 44.8 ± 7.9 kg/m(2) and 7.9 ± 4.5, respectively, received a vertical gastrectomy (76%) or Roux-en-Y gastric bypass (12%). Preoperatively, 30% of patients complained of excessive daytime sleepiness (ESS > 10). Patients with preoperative excessive daytime sleepiness were more obese (p = 0.002), had higher fasting glucose levels (p = 0.02), more likely to have a diagnosis of sleep-disordered breathing (p < 0.001), report snoring (p < 0.001), and had lower health-related quality of life measures particularly physical function (p < 0.001), depression (p = 0.006), and sexual satisfaction (p = 0.04) than non-sleepy patients. At 12-months postoperatively, most patients experienced a significant reduction in BMI (28.6 ± 5.5 kg/m(2), p < 0.001) and excessive daytime sleepiness (mean ESS 5.3 ± 3.3, p < 0.001). Patients with a clinically relevant improvement in the ESS at 12-months post-operatively had greater improvements in physical function (p = 0.009) and snoring (p = 0.010) and were more likely still using positive airway pressure therapy (p = 0.032) than patients without a clinically relevant improvement. Statistically and clinically significant improvements in all health-related quality of life measures were noted at 24 months. Bariatric surgery is associated with dramatic weight loss and improvements in physical functioning and daytime sleepiness.