The purpose of this study was to investigate the prediction of pain catastrophizing based on pain anxiety symptoms and cognitive flexibility in cancer patients Method and Materials: In this cross-sectional study all cancer patients in Tehran in 2021-22 were the target population. Among this population 250 cancer patients were selected via candidate and at reach sampling method. Then the selected patients completed the Paknejad et al.`s Pain Anxiety Symptoms (2014), Sullivan et al. `s Pain Catastrophizing Pain (1995), and Dennis et al.`s (2010) Cognitive Flexibility Questionnaire. For data analysis, Pearson correlation and step by step regression analysis were used. Data were analyzed by SPSS-24.Findings: There was a relationship between cognitive flexibility and pain anxiety symptoms with pain catastrophizing (P0.01>). The relationship between pain catastrophizing with pain anxiety symptoms was positive. However, there was a negative relationship between pain catastrophizing and cognitive flexibility. Moreover, catastrophizing pain could be predicted based on anxiety symptoms and cognitive flexibility. Conclusion: To conclude, it seems in cancer patients some cognitive factors have important roles in pain catastrophizing as pain anxiety symptoms and cognitive flexibility.