Aim: Hematopoietic Stem Cell Transplantation (HSCT) is preferred as an aggressive method for the treatment of hematologic cancers. High dose chemotherapy, isolation process and post-transplant complications are important sources of biopsychosocial stress for patients and their relatives. In the literature, the importance of providing psychiatric support and protecting mental health during the HSCT process is emphasized. In this context, this study aims to examine the changes in social support and mental health perceived by patients and their relatives during the HSCT process.