Objectives: Irritable bowel syndrome (IBS) is a frequently disabling and almost invariably distressing disease with a high overall prevalence. Numerous trials identified the importance of psychogenic and emotional etiological factors, and this is obvious in clinical practice. Although relaxation techniques are frequently recommended, there is still a lack of evidence for their efficacy in the management of IBS. This study therefore aims to determine the efficacy of functional relaxation (FR) in IBS. Subjects: The subjects were 80 patients with IBS. Interventions: Participants were randomly allocated either to FR or to enhanced medical care (EMC: treatment as usual plus two counseling interviews) as control intervention with 2 weekly sessions over the 5-week trial each. Thirty-nine (39) patients completed FR and 39 received EMC. Outcome measures: An impairment-severity score (IS) was employed as the primary outcome parameter with assessment at baseline, after treatment, and again after 3-month follow-up. Results: FR was significantly superior to EMC with a standardized effect size of 0.85. The achieved effects through FR remained stable in terms of psychic and bodily impairment after 3-month follow-up. Conclusions: The results of our trial suggest a positive effect of FR training on subjective functional impairment in the IS, if provided in addition to treatment as usual (TAU). There appears to be a clinically relevant long-term benefit of FR as a nonpharmacological and complementary therapy approach in IBS.