Purpose: Hematopoietic stem cell transplantation (HSCT) is an important treatment modality used in many benign and malignant diseases today. However, it can negatively affect life due to its side effects and increase the stress level of patients and their need for social support. In the literature, there is a need for studies about the coping styles and social support levels of cancer patients who are planning to have stem cell transplantation. This study was carried out to determine the social support levels and the styles of coping with stress of cancer patients with planned stem cell transplantation and to determine the relationship between them. Material and Methods: A total of 68 cancer patients participated in this study, which was planned with descriptive and correlational design. The "Patient Information Form", "Multidimensional Scale of Perceived Social Support" and "Styles of Coping with Stress" were used to collect data. Results: Cancer patients with planned stem cell transplantation perceived social support most from their significant other. Positive attitudes of the patients (self-confident, optimistic) in coping with stress were at high level, and negative attitudes (desperate, submissive, seeking social support) were at moderate level. As the age of the patients increased, their approach to seeking social support decreased (r=-0.240; p=0.049). The social lives of the patients were affected more compared to their work and family life during the disease, and those living in the nuclear family used positive approaches more in coping with stress (p