We conducted a case-control study in order to evaluate whether ABO gene polymorphisms were associated with a high risk of developing COVID-19 in a cohort of patients. Six ABO gene polymorphisms (rs651007 T/C, rs579459 T/C, rs495828 T/G, rs8176746 A/C, rs8176740 T/A, and rs512770 T/C) were determined using TaqMan genotyping assays in a group of 415 COVID-19 patients and 288 healthy controls. The distribution of rs651007 T/C, rs579459 T/C, rs495828 T/G, and rs8176746 A/C polymorphisms was similar in patients and healthy controls. Nonetheless, under co-dominant (OR = 1.89, pCCo-dominant = 6 × 10−6), recessive (OR = 1.98, pCRecessive = 1 × 10−4), and additive (OR = 1.36, pCAdditive = 3 × 10−3) models, the TT genotype of the rs8176740 T/A polymorphism increased the risk of developing COVID-19. In the same way, under co-dominant, recessive, and additive models, the TT genotype of the rs512770 T/C polymorphism was associated with a high risk of developing COVID-19 (OR = 1.87, pCCo-dominant = 2 × 10−3; OR = 1.87, pCRecessive = 5 × 10−4; and OR = 1.35, pCAdditive = 4 × 10−3, respectively). On the other hand, the GTC and GAT haplotypes were associated with a high risk of COVID-19 (OR = 5.45, pC = 1 × 10−6 and OR = 6.33, pC = 1 × 10−6, respectively). In addition, the rs8176740 TT genotype was associated with high-platelet plasma concentrations in patients with COVID-19. Our data suggested that the ABO rs512770 T/C and rs8176740 T/A polymorphisms increased the risk of developing COVID-19 and the plasma concentration of platelets.