Irritable bowel syndrome (IBS) is a disorder of the gut-brain interaction that is associated with abdominal pain, altered bowel patterns, and reduced quality of life. Up to 50% of patients with IBS also report anxiety or depressive symptoms. Although effective self-management interventions exist for individuals with IBS, few have been effectively implemented, and most do not consider the unique needs of patients with comorbid IBS and anxiety or depression. This study aimed to determine the anticipated acceptability, appropriateness, feasibility, and usability of a comprehensive self-management intervention using an implementation science and human-centered design approach among individuals with comorbid IBS and anxiety or depression and health care providers. A convergent mixed methods design was used to elicit feedback on the comprehensive self-management intervention outline and content to identify refinement needs before testing. Patients with IBS and moderate to severe anxiety or depression and health care providers were purposefully sampled from primary care and gastroenterology settings. Participants completed semistructured interviews and surveys on anticipated acceptability, appropriateness, feasibility, and usability. Patient participants (n=12) were on average 36.8 (SD 12.2) years of age, and 42% (5/12) were currently receiving psychological therapy. Health care providers (n=14) were from primary care (n=7) and gastroenterology (n=7) settings. The mean usability scores (out of 100) were 52.5 (SD 14.5) for patients and 45.6 (SD 11.6) for providers. For patients and providers, qualitative data expanded the quantitative findings for acceptability and appropriateness. Acceptability findings were the comprehensive nature of the intervention and discussion of the gut-brain interaction. For appropriateness, participants reported that the intervention provided structure, accountability, and support. Feasibility was confirmed for patients, but there was a divergence of findings between quantitative and qualitative measures for providers. Patients focused on intervention feasibility, while providers focused on implementation feasibility in the clinic. Identified usability issues to address before implementation included the intervention delivery format, length, and lack of integration into health care settings that, if not addressed, may limit the reach of the intervention. Patients and health care providers found the intervention acceptable and appropriate. Several feasibility and usability issues were identified, including intervention delivery methods, length of intervention, and the best methods to implement in the clinic setting. The next steps are to refine the intervention to address the identified issues and test in a pilot study whether addressing usability issues leads to the anticipated improvements in implementation and uptake.