ObjectivesTo evaluate content validity and psychometric properties of the 29-item Patient-Reported Outcomes Measurement Information System (PROMIS-29) to determine its suitability in inflammatory bowel disease (IBD) clinical trials. MethodsContent validity of PROMIS-29 was evaluated using qualitative interviews, including concept elicitation and cognitive debriefing, among patients living with Crohn’s disease (Crohn’s disease n = 20) or ulcerative colitis (UC, n = 19). PROMIS-29 validity, reliability, and responsiveness were assessed using data from phase II clinical trials of Crohn’s disease (N = 360) and UC (N = 518). ResultsCommon (≥74%) symptoms reported in qualitative interviews were increased stool frequency, fatigue, abdominal pain/cramping, blood/mucus in stool, bowel urgency, and diarrhea. Disease impact aligned with PROMIS-29 content (depression, anxiety, physical function, pain interference, fatigue, sleep disturbance, and ability to participate in social roles/activities). Cognitive debriefing indicated that PROMIS-29 instructions were easily understood, items were relevant, and the recall period was appropriate. Psychometric evaluations demonstrated that PROMIS-29 scores indicating worse symptoms/functioning were associated with lower health-related quality of life and greater disease activity and severity. PROMIS-29 domain scores correlated (rs ≥ 0.40) with IBD Questionnaire domains and EuroQol-5-Dimension-5-Level dimensions measuring similar concepts. Test-retest reliability among patients with stable disease was moderate-to-excellent (0.64-0.94) for nearly all domains in all studies. PROMIS-29 was responsive to change in disease status from baseline to week 12. Thresholds for clinically meaningful improvement ranged from ≥3 to ≥8, depending on domain. ConclusionsPROMIS-29 is valid, reliable, and responsive for assessing general health-related quality of life and treatment response in IBD clinical trials.