Investigation of supportive care needs of cancer patients is important to implement any supportive care programs. There is no relevant studies investigated supportive care needs of Iranian cancer patients and factors affecting such needs. So, the aims of present study were to determine the unmet supportive care needs of Iranian cancer patients and its predictive factors. In this descriptive- correlational study 274 cancer patients in one referral medical center in North West of Iran participated. For data collection, demographic and cancer related information checklist and Supportive Care Needs Survey (SCNS) was used. Logistic regression was used for data analysis of un-adjusted and adjusted Odds Ratios (ORs) for patients needs and analysis of variables of study based on Backward LR procedure SPSS Ver.13. More than fifty percent of participants reported unmet needs in 18 items of SCNS. Most frequent unmet needs were related to health system and information domains and most meet needs were related to sexuality and psychological domains. The result of logistic regression identified predictors of each domain of supportive care needs. The variable such as sex, age and living situation were most important predictors of unmet needs. The results showed that Iranian cancer patients have many supportive care needs in different domains. In general female cancer patients are at risk of more unmet supportive care needs. So, health care professionals should be more sensitive to fulfillment of supportive care needs of female.