BackgroundMore than 80% of patients seeking metabolic and bariatric surgery (MBS) report disturbance in sleep function. No studies have assessed the psychometric properties of sleep measures in MBS samples. ObjectivesThis study assessed the reliability and validity of the Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI) in a large sample of patients seeking MBS. SettingTwo academic medical centers. MethodsMeasures of sleep (PSQI & ISI) and psychological functioning, including the Quick Inventory of Depressive Symptomatology (QIDS), were administered pre-surgically. Internal consistency was assessed with mean inter-item correlations and item-total correlations. Construct validity was assessed using confirmatory factor analyses (CFAs) based on models identified in the literature and by measuring convergent and discriminant validity. ResultsParticipants (N = 939) were primarily female (83.4%) with a mean age of 41.7 (SD=11.5) years and mean BMI of 47.5 kg/m2 (SD = 8.5). CFAs indicated excellent fit for two-factor solutions for the PSQI and ISI. Internal consistency for the PSQI and ISI were acceptable. Convergent validity was demonstrated by large correlations between the PSQI and ISI (r = .80, p < .001), and moderate correlation between the PSQI, ISI, and QIDS (rs > .50, ps < .001). The PSQI and ISI were moderately correlated with QIDS items assessing sleep function (p < .001), but correlations with items assessing appetite change were small (r < .10), demonstrating good discriminant validity. ConclusionsResults support the reliability and validity of the PSQI and ISI for patients undergoing MBS.