Cancer is one of the life-threatening diseases. As diagnosis and treatment methods are improved leading to better survival rate of cancer cases. Loss of fertility is one of the severe and long-lasting complications of radiotherapy and chemotherapy for cancer treatment. As the oncologists are the only source of information for the cancer patients to be aware of fertility preservation methods, this nationwide survey was carried out to explore the extent of knowledge, practice pattern and attitudes of Iranian oncologists toward “fertility preservation” (FP). Methods: Oncologists recruited in this survey were Iranian specialists in radiation oncology and hematology attended four large and important national and international congresses and symposiums. Including criteria were current practice in the oncology ward and at least one year of working with cancer patients. Question types included yes/no, multiple choice and 4-point Likert. Result: A total mean knowledge of FP was 2.250 ±0.712 (ranging from none: 1 to high: 4). Highest knowledge among the participants were about “GnRH” (2.776±1.098) and “sperm cryopreservation” (2.646±1.003). In influencing factor on discussing FP with the patients, age was highest (3.75±0.538) and heredity scored lowest (2.98±0.869). Majority believed that the specialists will have responsibility if cancer patients lose their fertility because of the lack of information about FP options (71% vs. 29%). Only 11.7% of males and 16.3% of females provided their patients with written information about FP, while73.3% and 73.1% male and female participants referred cancer patients to reproductive specialists with no difference. Conclusion: Although the mean knowledge of oncologists was low, most of participants believed the importance of FP and discussing it with the patients. However, minority of them provided their patients with written information.