This multicenter, double-blind, randomized study compared the efficacy, pharmacokinetics (PKs)/pharmacodynamics (PDs), safety and immunogenicity profile of RTXM83 vs. reference rituximab (R-rituximab), both with CHOP, as first-line treatment of diffuse large B-cell lymphoma (DLBCL). A total of 272 patients <65 years of age, with good prognosis (136 per arm) were randomized (1:1) to receive six cycles of either RTXM83 or R-rituximab. The primary efficacy endpoint was achieved (overall response rate of 83.6% for RTXM83 and 82.9% for R-rituximab) with a difference 0.7% between arms (95%CI: [-8.77% to 10.17%]) fulfilling the predefined non-inferiority margin (-13%). Similar number of patients reported at least one adverse event (AE) (131 per arm) or one serious AE (47 with RTXM83 and 45 with R-rituximab). Anti-drug antibody development was comparable between the arms. PK/PD secondary endpoint results support similarity between the compounds. RTXM83 exhibits non-inferior efficacy and similar safety/immunogenicity to R-rituximab, being an accessible alternative for the treatment of patients with previously untreated DLBCL.