Background <p>Mindfulness-based interventions are recommended for improving well-being. We evaluated the potential added value of shared meditation involving patients with cancer, health professionals, and third persons compared with patient-only meditation.</p> Methods <p>We designed a randomised controlled trial (CONSORT guidelines) to assess the benefit of shared meditation, where patients with cancer (target population) were assigned to receive the meditation programme in groups involving caregivers and thirds persons (experimental arm) or in groups of patients only (control arm). The study involved 97 volunteers: 65 patients, 16 caregivers, and 16 third persons (neither carers nor patients). Patients were randomised between ‘Shared’ meditation (33 patients), and ‘Patient’ meditation (32 patients). A dedicated programme on mindfulness and compassion (12 weekly 2&#xa0;h-sessions and 2 half-day retreats) was administered. The primary endpoint was the sense of self-efficacy (Generalized Self-Efficacy Scale (GSES)). Perceived stress was measured by the Perceived Stress Scale (PSS), one of those subscales also focused on self-efficacy. Qualities of mindfulness, self-compassion, participants’ perception of change in their quality of life, and satisfaction following the programme were also assessed.</p> Results <p>Both patient arms experienced substantial improvement in self-efficacy scores (GSES) following the programme, without a significant difference between the arms. As secondary endpoints, perceived stress and mindfulness qualities were significantly improved in both arms, as well as several self-compassion dimensions (self-kindness, sense of common humanity, and mindfulness dimensions). Patients in the shared meditation arm showed a significant improvement in self-efficacy (PSS) and a reduction in feelings of isolation (self-compassion scale), which was not significant in patients in the patient-only arm. Patients greatly appreciated shared meditation, as evidenced by adherence to the programme and satisfaction assessments. Participants reported a perception of improvement in their quality of life.</p> Conclusion <p>The added value of shared meditation compared to patient-only meditation was not demonstrated in terms of sense of self-efficacy (GSES). Shared meditation specifically improved perceived self-efficacy (PSS subscale) and reduced the feeling of isolation. This approach could constitute a useful tool for patients to better cope with cancer and to break out of the context of illness, with the understanding that suffering is part of shared human experience.</p> Trial registration <p>ClinicalTrials.gov. NCT06041607, registered on 09/18/2023. <a href="https://clinicaltrials.gov/study/NCT06041607">https://clinicaltrials.gov/study/NCT06041607</a>.</p>