Treatment outcomes of malignant lymphoma have improved due to the discovery of novel chemotherapeutic and molecular targeted agents as well as advances in their combination uses. However, the prognosis of T-cell lymphoma remains poorer than that of B-cell lymphomas, and progress is slow. The reasons include their chemotherapeutic resistant nature and the absence of effective antibody agents for T-cell lymphomas. The number of T-cell lymphoma subtypes increased from 21 in the WHO classification 2008 to 29 in the WHO classification 2016. This means that T-cell lymphomas are heterogeneous. T-cell lymphomas can be divided to ALK-positive anaplastic lymphoma (ALCL) with a good prognosis and others with poorer prognoses. ALK-positive ALCL can be successfully treated with CHOP, but the others cannot. P-glycoprotein resistant anthracyclines, etoposide, or hematopoietic stem cell transplantations are increasingly applied to improve outcomes, but no standard treatment approach has yet been established. Regarding relapsed/refractory T-cell lymphoma, many novel agents are currently under development. The treatment outcomes of T-cell lymphoma need to be improved by applying innovative strategies including further novel agents.