Purpose: To explore participants' experiences and perspectives on the relevance and meaning of participating in the multimodal interdisciplinary rehabilitation programme named 'HAPPY', and the programme's influence on their handling of everyday life during and after non-myeloablative allogeneic haematopoietic stem cell transplantation. Method: A qualitative interview study using Thorne's interpretive description methodology. A semi-structured interview guide and the analysis were inspired by symbolic interactionism. From April to July 2020, individual interviews were conducted with 24 patients who had participated in HAPPY while undergoing non-myeloablative haematopoietic stem cell transplantation. Results: HAPPY contributed to the patients’ knowledge building on the basis of three themes: Social Solidarity and Comparison, Processing Mind and Body, and Balancing Disease and Life. HAPPY supported the participants in maintaining their physical functioning and induced a perception of empowerment. Moreover, HAPPY supported patients in their efforts to familiarise themselves with their changed life conditions after the stem cell transplantation. Conclusion: Our findings showed that participation in HAPPY empowered patients to manage and cope with the stresses of everyday life and restore balance in their lives whilst undergoing treatment and confronting their cancer diagnosis. The findings underline the importance of elements of peer support and continuous support and facilitation from the specialist team, and the possibility to rethink the use of online technology to support and ensure a balance between disease and life and to minimise hospital visits.