Background: Glofitamab is a bispecific antibody engaging CD3 on T-cells and CD20 on B-cells. Glofitamab is approved for the treatment of relapsed, refractory diffuse large B-cell lymphoma (R/R DLBCL). Lymphocyte-activation gene 3 (LAG3) and T-lymphocyte-associated protein 4 (CTLA4) are immune checkpoint receptors with inhibitory effects on T-cell activity. There are several common germline variants of both receptor genes. Methods: Here, we evaluate clinical outcomes in R/R DLBCL patients treated with glofitamab according to the single-nucleotide polymorphisms LAG3 rs870849 and CTLA4 rs231775. Results: While there was no apparent association of CTLA4 genotype with glofitamab treatment outcomes, significant differences emerged in LAG3 rs870849 carriers with extended progression-free and overall survival in homozygous LAG3 T455, intermediate PFS and OS in heterozygous LAG3 I455T, and short PFS and OS in homozygous LAG3 I455 carriers. Conclusions: LAG3 rs870849 may be a prognostic response marker in R/R DLBCL treated with glofitamab.