Aims: Irritable bowel syndrome is a disorder of gut–brain interaction in which health anxiety and impaired quality of life are prominent. To evaluate the effectiveness of a single-session therapy based on cognitive-behavioral stress management principles on health anxiety and quality of life in patients with IBS.

Materials & Methods: In a quasi-experimental pretest–posttest–follow-up design, 30 patients with IBS were purposively sampled from gastroenterology and psychology clinics in Gilan and Rasht, Iran (January–March 2026) and randomly assigned to an intervention or control group. The sample comprised 30 patients; 27 participants completed all study assessments (intervention n = 13, control n = 14). The intervention group received one 90–120-minute session. Measures were the Short Health Anxiety Inventory (SHAI) and the World Health Organization Quality of Life-BREF (WHOQOL-BREF). All statistical analyses were performed using SPSS (Version 27) and JASP (Version 0.19.0).

Findings: The time × group interaction was significant for health anxiety (F = 14.887, p < .001, η² = .383): SHAI scores in the intervention group declined from 26.69 (pretest) to 23.77 (posttest) and 21.23 (follow-up). Significant interactions were also found for SF-36 vitality (F = 30.592, p < .001, η² = .560) and social functioning (F = 14.589, p < .001, η² = .378), with intervention participants improving at posttest and follow-up while controls remained unchanged.

Conclusion: The findings suggest that a single-session therapy based on cognitive-behavioral stress management principles may reduce health anxiety and improve selected aspects of quality of life in patients with IBS.