The prognostic role of TP53 mutations in patients with diffuse large B-cell lymphoma (DLBCL) treated with R-CHOP chemotherapy is undefined. In a large patient cohort study, those with TP53 mutations had worse progression-free and overall survival, and mutant TP53 was predictive of treatment outcome in patients with the germinal centre B-cell and activated B-cell subtypes; underscoring TP53 stratification potential in these patient subsets.