Background: The Moorehead-Ardelt II (MA-II) questionnaire is the most frequently applied instrument to assess quality of life (QoL )in bariatric surgery patients. Our aim was to validate the Czech, German, Italian, and Spanish version of the MA-II. Methods: A total of 893 patients were enroled in a prospective cross-sectional European study. Two thirds of the patients (n = 591) were postsurgical cases. In addition to demographic and clinical data, QoL data was collected using the MA-II questionnaire, the EuroQoL-5D (EQ-5D),and the Short Form 36 Health Survery (SF-36). Statistical parameters for contingency (Cronbach’s alpha),construct and criterion validity (Pearson’s r),and responsiveness (standardised effect sizes) were calculated for each language version. Results: In the different languages, Cronbach’s alpha ranged from 0.817 to 0.885 for the MA-II. These values were higher than those obtained for the SF-36 (0.418–0.607). The MA-II was well correlated to the EQ-5D (r = 0.662) and to 3 of the 8healthdomains of the SF-36 (0.615, 0.548, and 0.569 for physical functioning, physical role, and general health, respectively). As expected, there was a negative correlation between the MA-II and the BMI (r = –0.404 for all patients), but no significant correlation with age was found. When comparing both the heaviest and the lightest third of the patients, mean responsiveness was higher for the MA-II (–1.138) than for the domains of the SF-36 (range –0.111 to –1.070) and the EQ-5D (–0.874). Conclusion: The Czech, German, Italian, and Spanish version of the MA-II questionnaire are valid instruments and should be preferred to generic questionnaires as they provide better responsiveness.