AbstractBackgroundWomen with endometriosis suffer from frequent symptoms despite multiple treatments in tertiary care. Although there is a need for a biopsychosocial perspective on endometriosis treatment, few conservative treatments have been investigated. We aimed to investigate the effects of a brief Mindfulness‐Based Intervention (bMBI) in women with deep endometriosis who remain symptomatic despite undergoing conventional medical treatment.MethodsA randomized controlled trial was performed with two groups: a standard medical treatment plus bMBI program and only standard medical treatment as a control. A total of 63 eligible participants were randomized to bMBI and control groups. The primary outcome was endometriosis‐related pain, and secondary outcomes were quality of life and stress perception post‐treatment. Analyses were carried out using multiple regression models.ResultsThe results show that bMBI significantly improved pain unpleasantness (Cohen's f2 = 0.67, NNT = 3.2), pelvic pain (Cohen's f2 = 0.16, NNT = 5.3) and dyschezia (Cohen's f2 = 0.23, NNT = 2.9) immediately post‐treatment and decreased all endometriosis‐related pain (Cohen's f2 ranging from 0.20 to 0.60 and NNT ranging from 5 to −9) after the follow‐up. We found an extensive positive effect of bMBI on the mental health dimension in the two time point measures (Cohen's f2 = 0.34 and 0.25, NNT = 3.5 and 2.3) and vitality (Cohen's f2 = 0.22, NNT = 2.1) after the follow‐up.ConclusionsOur study suggests that bMBI is useful for managing endometriosis‐related pain and restoring women's psychological well‐being.SignificanceBrief Mindfulness‐Based Intervention (bMBI) improved endometriosis‐related pain and mental health compared to standard medical care. The present findings contribute to the applicability of MBI in visceral pain patients.