Breast cancer (BC) does not affect ethnic groups equally. BC mortality is higher in Israeli Palestinian Arab women than among Israeli Jewish women. This study aims to compare clinical, biological and pathological characteristics of breast cancer in the two populations. Records of 1,140 women with BC treated at Northern Israel between 2002 and 2007 were reviewed: 872 Jews and 268 Arabs. Age at diagnosis, tumor stage, pathological differentiation, estrogen receptor (ER) and HER-2 expression were evaluated. The main age at diagnosis was 49.9 years for Arabs and 59.4 years for Jews (p < 0.0001). Mean tumor size was < 2 cm in 25% of Arabs and 53% of Jews (p < 0.0001). Lymph node metastases presented in 64.6% of Arabs and 37.2% of Jews (p < 0.0001). Stage I disease was 19% in Arab and 49.2% in Jewish women while Stages III and IV disease was 42% and 11.3% respectively (p < 0.001). ER was positive in 69% of Arabs and in 78.5% of Jews (p < 0.001). Poorly differentiated tumors were found in 28.8% of Arabs vs. 12.8% in Jews (p < 0.0001). Overexpression of HER-2 was present in 35.4% of Arab and 22% of Jewish women (p < 0.001). We found that race is an important predictive factor for breast cancer. Arab women are diagnosed at younger age, with more advanced stage and biologically more aggressive disease than in Jewish women. Socioeconomic factors alone are not sufficient to explain significant effects of race on tumor characteristics. Findings suggest a different genetic susceptibility in the two populations which needs further research.