The aim of this study was to gain insight into the relationship between spiritual well-being in breast cancer patients, psychological flexibility, social support, and personality traits. The research was conducted on 64 women (Mage=58.36, SD=11.30), while undergoing radiation therapy. Results showed that younger, less agreeable, and more conscientious patients were more likely to experience positive changes in life after the illness; greater perceived social support positively predicted sense of purpose/reason for being alive, and younger, more open to experience patients tended to be more hopeful. Full mediation effect of perceived social support was found – participants who were more agreeable and open to experience, through greater perceived support, achieved a higher sense of purpose/reason for being alive, while conscientious and psychologically inflexible individuals perceived less support, which resulted in diminished sense of purpose. Our results highlight the pivotal role of perceived social support, which could modulate and diminish negative psychological, spiritual and existential consequences of breast cancer.