Objective: We aimed to delineate the effects of the ABO groups and the main clinical outcomes with the current SARS-CoV-2 variants, i.e., delta and omicron. Materials and Methods: In this retrospective case-control study, the total 360 adult COVID-19 patients who were followed in the pandemic waves of delta and omicron variants and had ABO blood group analysis were included and divided into two groups according to the waves of variant. Demographic characteristics, comorbidities, length of hospitalization and intensive care needs, survival and ABO groups of cases were recorded. These groups were then compared with the ABO group distribution of population-reflecting 1881 healthy individuals and 186 historical alpha variant cases. Results: The demographic characteristics of the case groups and control group were similar. ABO distributions of the delta and omicron wave groups compared to the control group did not show a statistically significant difference. While advanced age (p<0.001) and presence of comorbidity (p=0.006) showed statistically significant differences in terms of overall survival, ABO blood group was not found to be a risk factor for mortality (p=0.114 in delta, and 0.526 in omicron), hospitalization time (p=0.148 in delta, p=0.224 in omicron), and intensive care unit admission (p=0.096 in delta, p=0.229 in omicron). Conclusion: The risk of infection among ABO blood groups, which has been shown in previous studies for the alpha variant against group A and in favor of group O, does not appear to be valid for delta and omicron period patients. Therefore, the anti-infective measures, especially vaccination, should not differ for individuals according to ABO blood group.