Diffuse large B cell lymphoma (DLBCL) is one of the most prevalent lymphoid malignancies. The current standard of care can cure about two-thirds of DLBCL patients. Primary testicular diffuse large B-cell lymphoma (PT-DLBCL) is a rare but highly aggressive form of mature B-cell lymphoma that accounts for approximately 1%-9% of testicular malignancies. Different from nodal DLBCL, PT-DLBCL has a markedly worse prognosis because of inferior response to the current treatment regimens and significant extranodal tropism. Three main questions remained unresolved in the field of PT-DLBCL research. Previously, two prognostically important categories of DLBCL have been defined: activated B cell-like (ABC) DLBCL and germinal center B cell-like (GCB) DLBCL. Most PT-DLBCLs were classified as ABC-DLBCL. However, the exact cells of origin (COO) of PT-DLBCL were still under debate. Secondly, the lack of transcriptomics profiling of PT-DLBCL at the single-cell level hindered the discovery of intra-tumor heterogeneity. Finally, the role of the testis microenvironment in PT-DLBCL was unclear. Herein, we performed single-cell RNA sequencing (scRNASeq) and bulk whole exome sequencing (WES) to reveal the molecular landscape of PT-DLBCL. We defined predictive signatures based on gene profiles of the pivotal clusters. Our study could be a benefit for the clinical classification of PTDLBCL and provide valuable therapeutic targets.