ABO blood type has been observed in previous studies to be associated with the risk of certain malignancies, including pancreatic and gastric cancer. Our aim is to explore the possible relationships between blood groups and characteristics of patients and whether it is associated with the risk of breast cancer. Our study consisted of 160 breast cancer patients with serologically confirmed ABO blood group. A group of 92 healthy blood donors was identified as a control group. Overall distribution of ABO blood groups was comparable between patients (53.1% A, 21.8% O, 17.5% B and 7.5% AB) and controls (39.1% A, 32.6% O, 18.4% B and 9.7% AB). There were no significant differences in clinicopathologic characteristics among patients with different ABO blood groups. We found that patients with A blood group was positively associated with the risk of breast cancer (adjusted Odds Ratio=2.13, 95% Confidence Interval=1.04-2.96, P=0.03). We conclude that A blood type was associated with increased the risk of breast cancer and it might increase the probability to generate high-risk individuals if further studies confirm the present preliminary findings.