Background and Objectives: Demoralization syndrome causes loss of meaning in life, hopelessness, and sense of failure. On the other hand, understanding religious coping can affect the communication and presentation ways of religious strategies in patients with cancer. It seems that the posttraumatic growth contributes to a person's psychological adjustment to cancer. Therefore, the aim of current study was the prediction of posttraumatic growth on the base of demoralization syndrome and religious coping among cancer patients. Materials and Methods: In this descriptive study, based on the criteria for entering the study and by using convenient sampling, 167 patients referred to Reza Radiotherapy and Oncology Center in Mashhad, filled the research materials in 2018. Data were collected by a demographic questionnaire, Posttraumatic Growth Inventory (PTGI), Demoralization Syndrome Scale (DS) and the Brief Religious Coping Questionnaire (RCOPE) and analyzed by Pearson's correlation coefficient and multiple linear regression analysis using the stepwise method. Results: There was a significant negative relationship between components of dysphoria (r=-0. 306, p= 0. 001), disheartenment (r=-0. 296, p= 0. 001) and sense of failure (r=-0. 251, p= 0. 001) and posttraumatic growth and there was a significant positive relationship between positive religious coping (r= 0. 215, p= 0. 005) and posttraumatic growth. Also, multiple linear regression results showed that totally 21 percent variance of posttraumatic growth was explained by predictive variables. Conclusion: According to the results, it seems that the prevention of demoralization syndrome, and using positive religious coping strategies as effective ways can help to increase posttraumatic growth in cancer patients.