Background: Despite the remarkable development of medical sciences, cancer has yet remained one of the most important diseases of the current century and the second cause of death following cardiovascular diseases. Although we witnessed considerable development in treating cancer and increased number of survivors, cancer is a unique disease that makes the patients deeply feel helplessness and fear. Methods: A qualitative content analysis research was done. The present study investigated patients' experience and behaviors after hearing about their cancer. Purposeful sampling was carried out and continued until data saturation. We used qualitative validation methods to verify the results. Results: Study participants consisted of 14 patients. 10 main components emerged from the data including: 1) getting shocked, 2) fear, 3) anxiety and stress, 4) guilt, 5) hopelessness, 6) depression, 7) isolation, 8) lack of affection and dependency on family members, 9) getting prepared to die and, 10) reviving spiritual relationship with God. Conclusions: There is a necessity to understand the mental feelings of cancer patients, and program suitable clinical interventions based on patients' mental needs. As the number of cancer patients is increasing, the results of the present study can be useful for patients' families and clinical personnel especially physicians and nurses in dealing with cancer patients.