The human immunoglobulin heavy-chain (IGH) locus is exceptionally polymorphic, with high levels of allelic and structural variation. Thus, germline IGH genotypes are personal, which may influence responses to infection and vaccination. For an improved understanding of inter-individual differences in antibody responses, we isolated SARS-CoV-2 spike-specific monoclonal antibodies from convalescent health care workers, focusing on the IGHV1-69 gene, which has the highest level of allelic variation of all IGHV genes. The IGHV1-69∗20-using CAB-I47 antibody and two similar antibodies isolated from an independent donor were critically dependent on allele usage. Neutralization was retained when reverting the V region to the germline IGHV1-69∗20 allele but lost when reverting to other IGHV1-69 alleles. Structural data confirmed that two germline-encoded polymorphisms, R50 and F55, in the IGHV1-69 gene were required for high-affinity receptor-binding domain interaction. These results demonstrate that polymorphisms in IGH genes can influence the function of SARS-CoV-2 neutralizing antibodies. Display omitted •IGH genes with high allelic diversity are used in anti-SARS-CoV-2 antibodies•IGH allele usage can influence the activity of neutralizing antibodies•Cryo-EM analysis confirms the role of germline-encoded residues in antigen binding•IGH genotyping can uncover differences in Ab responses due to allelic variation The genes and alleles of the antigen receptor loci are highly variable between individuals, which may affect the quality of the immune response to different pathogens. Here, Pushparaj et al. use immunoglobulin genotyping and monoclonal antibody engineering to illustrate how heritable differences in such genes can modulate anti-SARS-CoV-2 antibody function.