Obesity has a negative impact on health-related quality of life (HRQoL). The SCALE Obesity and Prediabetes study investigated the effect of liraglutide 3.0 mg, as adjunct to diet and exercise, on HRQoL in patients with obesity [body mass index (BMI) ≥ 30 kg m−2] or overweight (BMI ≥ 27 kg m−2) with comorbidity. Participants were advised on a 500 kcal d−1 deficit diet and a 150-min week−1 exercise programme and were randomised 2:1 to once-daily subcutaneous liraglutide 3.0 mg or placebo. HRQoL was assessed using the Impact of Weight on Quality of Life-Lite (IWQOL-Lite) and Short-Form 36 (SF-36) v2 health questionnaires. Individuals on liraglutide 3.0 mg (n = 2046) had significantly greater improvements in IWQOL-Lite total score (10.6 ± 13.3) vs. placebo (n = 1020) (7.7 ± 12.8) and SF-36 physical (PCS) and mental (MCS) component summary scores (PCS, 3.6 ± 6.8; MCS, 0.2 ± 8.1) vs. placebo (PCS, 2.2 ± 7.7; MCS, −0.9 ± 9.1). The estimated treatment differences were IWQOL-Lite total score 3.1 (95% CI: 2.2; 4.0), P < 0.0001; SF-36 PCS 1.7 (95% CI: 1.2; 2.2), P < 0.0001 and MCS 0.9 (95% CI: 0.3; 1.5), P = 0.003. All subscales of the IWQOL-Lite and SF-36 were significantly improved with liraglutide 3.0 mg vs. placebo. More patients on liraglutide 3.0 mg experienced meaningful improvement on the IWQOL-Lite total (P < 0.0001) and the SF-36 PCS (P < 0.0001) scores.