Background: Numerous studies have documented the association of the ABO blood groups with the occurrence of cancers. Aim was to find out an association of ABO blood groups and various cancers in the North Eastern region of India.Methods: The study was a retrospective observational study that included 1000 cases and 1000 controls. The data included the ABO blood typing of the selected cancer sites which were head and neck, esophagus, stomach, breast, cervix, and ovary. Patients who attended blood bank of regional cancer center with requisition for blood transfusion from 2014 to 2016 were included. The control group was healthy blood donors. Chi square test was used to assess the difference among the compared groups. Risk was calculated by regression analysis. P value <0.05 was considered as statistically significant at 95% confidence interval.Results: Out of 1000 cases and 1000 controls, O blood group were seen in 377 (37.7%) and 395 (39.5%) cases and control, respectively. Significant reduced odds ratio (OR) in non O blood groups for head and neck, esophagus, stomach, and breast was observed. In case of carcinoma cervix, OR for B group was 1.5 (P=0.05), and for blood group A OR=2.2 (P=0.02) was seen in carcinoma ovary.Conclusions: In the studied population, patients with O blood group are at an increased risk of developing head and neck, esophagus, stomach, and breast cancers.