BACKGROUND & AIMS: There is an urgent need for safe treatments for irritable bowel syndrome (IBS) that relieve treatment-refractory symptoms and their societal and economic burden. Cognitive behavior therapy (CBT) is an effective treatment that has not been broadly adopted into routine clinical practice. We performed a randomized controlled trial to assess clinical responses to home-based CBT compared with clinic-based CBT and patient education. METHODS: We performed a prospective study of 436 patients with IBS, based on Rome III criteria, at 2 tertiary centers from August 23, 2010, through October 21, 2016. Subjects (41.4 ± 14.8 years old; 80% women) were randomly assigned to groups that received the following: standard-CBT (S-CBT, n = 146, comprising 10 weekly, 60-minute sessions that emphasized the provision of information about brain-gut interactions; self-monitoring of symptoms, their triggers, and consequences; muscle relaxation; worry control; flexible problem solving; and relapse prevention training), or 4 sessions of primarily home-based CBT requiring minimal therapist contact (MC-CBT, n = 145), in which patients received home-study materials covering the same procedures as S-CBT), or 4 sessions of IBS education (EDU, n = 145) that provided support and information about IBS and the role of lifestyle factors such as stress, diet, and exercise. The primary outcome was global improvement of IBS symptoms, based on the IBS-version of the Clinical Global Impressions-Improvement Scale. Ratings were performed by patients and board-certified gastroenterologists blinded to treatment allocation. Efficacy data were collected 2 weeks, 3 months, and 6 months after treatment completion. RESULTS: A higher proportion of patients receiving MC-CBT reported moderate to substantial improvement in gastrointestinal symptoms 2 weeks after treatment (61.0% based on ratings by patients and 55.7% based on ratings by gastroenterologists) than those receiving EDU (43.5% based on ratings patients and 40.4% based on ratings by gastroenterologists) (P < .05). Gastrointestinal symptom improvement, rated by gastroenterologists, 6 months after the end of treatment also differed significantly between the MC-CBT (58.4%) and EDU groups (44.8%) (P = .05). Formal equivalence testing applied across multiple contrasts indicated that MC-CBT is at least as effective as S-CBT in improving IBS symptoms. Patients tended to be more satisfied with CBT vs EDU (P < .05) based on immediate posttreatment responses to the Client Satisfaction Questionnaire. Symptom improvement was not significantly related to concomitant use of medications. CONCLUSIONS: In a randomized controlled trial, we found that a primarily home-based version of CBT produced significant and sustained gastrointestinal symptom improvement for patients with IBS compared with education. Clinicaltrials.gov no.: NCT00738920.