Objectives: To investigate the level and determinants of posttraumatic growth in Iranian cancer patients. Materials and Methods: This descriptive-correlational design study was conducted within a university-affiliated oncology hospital in Iran. A convenience sample of 450 patients with a definitive diagnosis of cancer of any type completed a demographic questionnaire and a posttraumatic growth inventory. Some disease-related information was obtained from patients' medical records. Results: The mean of posttraumatic growth reported by participants was 76.1. There was a statistically significant association between experience of posttraumatic growth and age (r = − 0.21, P=0.001), education at university level (F = 8.9, P=0.001) and history of treatment by radiotherapy (t = 2.1, P=0.03). Conclusion: The findings of this study suggest that Iranian cancer patients experience a moderate to high level of posttraumatic growth and confirm the hypothesis that the level of posttraumatic growth in non-Western cancer patients is more than that of Western cancer patients. Although, assessing the reasons for this difference needs more investigations.