STUDY QUESTION Does the Mind/Body Program for Infertility (MBPI) perform better, due to certain distinctive elements, than a partly matched support group in improving the wellbeing and medically assisted reproduction (MAR) outcomes of women with elevated distress levels in a clinical setting? SUMMARY ANSWER While robust enhancements occurred in the wellbeing overall, the cognitive behavioural and formalized stress management elements of the MBPI allowed a significantly stronger improvement in trait anxiety, but not in other mental health and MAR outcomes, compared with a support group. WHAT IS KNOWN ALREADY Mind-body psychological programmes adjacent to MAR have been found to improve women's mental states and possibly increase chances of pregnancy. However, not enough is known about the programme's effectiveness among patients with elevated distress levels in routine clinical settings, nor is it clear which of its particular ingredients are specifically effective. STUDY DESIGN, SIZE, DURATION A pre-post design, single-centre, randomized controlled trial was performed between December 2019 and October 2022 (start and end of recruitment, respectively). The sample size (n = 168) was calculated to detect superiority of the MBPI in improving fertility-related quality of life. Randomization was computer-based, with random numbers concealing identities of patients until after allocation. PARTICIPANTS/MATERIALS, SETTING, METHODS The trial was conducted at a large university teaching hospital. A total of 168 patients were randomly assigned to the mind-body (MBPI) group (n = 84) and the fertility support (FS) control group (n = 84). Patients received a 10-week, 135-min/week group intervention, with the FS group following the same format as the MBPI group, but with a less restricted and systematic content, and without the presumed effective factors. The number of patients analysed was n = 74 (MBPI) and n = 68 (FS) for post-intervention psychological outcomes, and n = 54 (MBPI) and n = 56 (FS) for pregnancy outcomes at a 30-month follow-up. MAIN RESULTS AND THE ROLE OF CHANCE Significant improvements occurred in both groups in all psychological domains (adjusted P < 0.001), except for treatment-related quality of life. Linear mixed-model regression analysis did not reveal significantly greater pre-post improvements in the MBPI group than in the FS group in fertility-related quality of life (difference in differences (DD) = 4.11 [0.42, 7.80], d = 0.32, adjusted P = 0.124), treatment-related quality of life (DD = −3.08 [−7.72, 1.55], d = −0.20, adjusted P = 0.582), infertility-specific stress (DD = −2.54 [−4.68, 0.41], d = −0.36, adjusted P = 0.105), depression (DD = −1.16 [3.61, 1.29], d = −0.13, adjusted P = 0.708), and general stress (DD = −0.62 [−1.91, 0.68], d = −0.13, adjusted P = 0.708), but it did show a significantly larger improvement in trait anxiety (DD = −3.60 [−6.16, −1.04], d = −0.32, adjusted P = 0.042). Logistic regression showed no group effect on MAR pregnancies, spontaneous pregnancies, or live births. LIMITATIONS, REASONS FOR CAUTION The follow-up only covered MAR-related medical outcomes and no psychological variables, and their rates were not equal in the two groups. Biological factors other than age, aetiology, and duration of infertility may have confounded the study results. Loss to follow-up was between 5% and 10%, which may have led to some bias. WIDER IMPLICATIONS OF THE FINDINGS The psychologically and medically heterogeneous sample, the normal clinical setting and the low attrition rate all raise the external validity and generalizability of our study. The MBPI works not only in controlled conditions, but also in routine MAR practice, where it can be introduced as a cost-effective, low-intensity psychological intervention, within the framework of stepped care. More studies are needed to further identify its active ingredients. STUDY FUNDING/COMPETING INTEREST(S) The authors received no financial support for the research, authorship, and/or publication of this article. The authors have no conflict of interest to disclose. TRIAL REGISTRATION NUMBER ClinicalTrials.gov NCT04151485. TRIAL REGISTRATION DATE 5 November 2019. DATE OF FIRST PATIENT'S ENROLMENT 15 December 2019. [ABSTRACT FROM AUTHOR]