Aims: The present study aimed to identify the most associated risk factors of breast cancer in Ilam province in 2015–2016. Materials & methods: In this case–control study, the case group consisted of 50 women with breast cancer with a definitive diagnosis from date 23 September 2015 to 22 September 2016. The two groups were group matched in terms of age. Data were collected through interviews and medical records. Results: According to the results, there was a significant relationship between the disease status and variables of family history, history of irregular menstrual cycles, history of breastfeeding, menopausal status, history of oral contraceptive pill consumption, BMI, menarche and number of pregnancies (p < 0.05). Conclusion: Regarding decisive risk factors of breast cancer, more studies with larger sample sizes that take into account more risk factors are necessary.