Summary T-cell and natural-killer (NK)-cell lymphomas are neoplasms with geographical variations in frequencies. T-cell lymphomas are more prevalent in Asia than in Europe and North America, and NK-cell lymphomas occur almost exclusively in Asia and South America. These low frequencies mean that the diagnosis and optimum treatment of patients with T-cell and NK-cell lymphomas have not been studied prospectively in randomised controlled trials. Because T-cell and NK-cell lymphomas are more prevalent in Asia, the establishment of management recommendations by Asian oncologists in collaboration with international experts is pertinent. This review outlines guidelines commensurate with different levels of health-care resources and expertise. Consensus statements were formulated for diagnosis, staging, follow-up, and treatment approaches in patients with T-cell and NK-cell lymphomas—aimed at unifying the design of studies and interpretation of results. For patients not in clinical trials, consensus opinions offer useful guidelines on optimum management.