Adult T-cell leukemia/lymphoma (ATL) is a peripheral T-cell malignancy associated with HTLV-1 infection. To decipher the genetic landscape of ATL, we performed an integrated molecular analysis, which included whole-genome, whole-exome, transcriptome and targeted sequencing, as well as array-based copy number and methylation analyses. The somatic alterations are highly enriched for T-cell receptor/NF-κB signaling, the G-protein coupled receptor associated with T-cell migration, and other T-cell-related pathways as well as immune surveillance related genes. Among these, PLCG1, PRKCB, CARD11, VAV1, IRF4, CCR4, and CCR7 activating mutations and CTLA4-CD28 and ICOS-CD28 fusion genes have been identified. In addition, these genes significantly overlap with HTLV-1 Tax interactome. These results provide an important basis for the development of new ATL diagnostics and therapeuticsregimens.