In this study we assessed the dietary phytochemical index in relation to the risk of breast cancer in women. This case-control study was conducted on 100 incident breast cancer cases and 175 healthy controls. Data regarding socio-demographic factors, medical history, medications, and anthropometric measurements were collected. Dietary data were obtained using a validated food frequency questionnaire and a energy-adjusted dietary phytochemical index (PI) was calculated. The odds ratios of breast cancer were assessed across energy- adjusted PI quartile categories. The mean age of participants was 46.2±8.9 and 45.9±9.4 years in cases and controls, respectively. The mean PI across quartile categories was 13.9±2.6, 21.1±1.8, 26.7±2.1, 41.6±10.2 in the first, second, third and fourth quartiles, respectively. After adjustment for all potential confounders, the risk of breast cancer in the forth quartile of dietary PI was significantly decreased (OR=0.08, 95%CI=0.01-0.84). Higher intake of phytochemical-rich foods is associated with lower risk of breast cancer.