He is a social epidemiologist and experimental social scientist specialized in social network and behavioral intervention. His current areas of research include improving economic inequality and well-being inequality in online social networks (e.g. Nishi et al, Nature, 2015; Nishi and Christakis, PNAS, 2015; Nishi et al, Sci Rep, 2016); promoting helmet use in motor cycle users among Asian countries by social network techniques; and understanding health inequality by evolutionary perspectives (e.g. Nishi, Soc Sci Med, 2015). He has also been interested in health services research in Asian countries including Japan and Thailand (e.g. Tamiya et al, Lancet, 2011; Nishi et al, Bulletin of WHO, 2012).