Here, we developed a novel CD5 gene expression signature as a biomarker of response to BTKi-based therapy in DLBCL....CD5 expression was observed in 12% of non-GCB DLBCLs. CD5+ DLBCLs displayed transcriptional features of B-cell receptor (BCR) activation and were enriched for BCR-activating mutations known to correlate with BTKi sensitivity.