Background: Avoidant/restrictive food intake disorder (ARFID) symptoms are common (up to 40%) among adults with disorders of gut-brain interaction (DGBI), but treatments for this population (DGBI + ARFID) have yet to be evaluated. We aimed to identify initial feasibility, acceptability, and clinical effects of an exposure-based cognitive-behavioral treatment (CBT) for adults with DGBI + ARFID., Methods: Patients (N = 14) received CBT as part of routine care in an outpatient gastroenterology clinic. A two-part investigation of the CBT included a retrospective evaluation of patients who were offered a flexible (8-10) session length and an observational prospective study of patients who were offered eight sessions. Feasibility benchmarks were ≥75% completion of sessions, quantitative measures (for treatment completers), and qualitative interviews. Acceptability was assessed with a benchmark of ≥70% patients reporting a posttreatment satisfaction scores ≥3 on 1-4 scale and with posttreatment qualitative interviews. Mixed model analysis explored signals of improvement in clinical outcomes., Results: All feasibility and acceptability benchmarks were achieved (and qualitative feedback revealed high satisfaction with the treatment and outcomes). There were improvements in clinical outcomes across treatment (all p's < .0001) with large effects for ARFID fear (-52%; Hedge's g = 1.5; 95% CI = 0.6, 2.5) and gastrointestinal-specific anxiety (-42%; Hedge's g = 1.0; 95% CI = 0.5, 16). Among those who needed to gain weight (n = 10), 94%-103% of expected weight gain goals were achieved., Discussion: Initial development and testing of a brief 8-session CBT protocol for DGBI + ARFID showed high feasibility, acceptability, and promising clinical improvements. Findings will inform an NIH Stage 1B randomized control trial., Public Significance: While cognitive-behavioral treatments (CBTs) for ARFID have been created in outpatient feeding and eating disorder clinics, they have yet to be developed and refined for other clinic settings or populations. In line with the recommendations for behavioral treatment development, we conducted a two-part investigation of an exposure-based CBT for a patient population with high rates of ARFID-adults with disorders of gut-brain interaction (also known as functional gastrointestinal disorders). We found patients had high satisfaction with treatment and there were promising improvements for both gastrointestinal and ARFID outcomes. The refined treatment includes eight sessions delivered by a behavioral health care provider and the findings reported in this article will be studied next in an NIH Stage 1B randomized controlled trial., (© 2022 Wiley Periodicals LLC.)