The aim was to synthesise patients’ and relatives’ experiences of participating in a psychosocial intervention related to having cancer. The study was a meta-synthesis inspired by Noblit & Hare's ‘meta-ethnography’ approach. We systematically searched six databases and included 33 studies in the meta-synthesis. Inclusion criteria were qualitative studies with relevance to the synthesis topic. The meta-synthesis conceptualised the way in which participants develop their way of living with cancer, and the role psychosocial interventions play in helping them to live through the illness. Five themes symbolising the participants’ core experiences were identified: (1) Emotional relief and a sense of well-being, (2) normalisation of experiences and a sense of control, (3) shared experience and a sense of community, (4) a safe place and (5) transformation and adaptability. The findings indicated that psychosocial interventions were used to try to deal with the changes in the human conditions caused by cancer. Sharing their experiences and forming social relationships helped the participants adapt to cancer. An existential perspective may provide a nuanced understanding of patients’ and relatives’ experiences of participating in psychosocial interventions.