In aging and aged countries, one of the main issues is to establish sufficient nursing homes for seniors. Japan, as one of the most rapidly aged countries, has been reforming nursing homes for the elderly since the 1990s and established a long‐term care insurance system. The purpose of this scoping review is to systematically map the evolution of researches for nursing homes in Japan since the 1990s, particularly with the post‐occupancy evaluation of the introduction of private rooms and small units. Forty‐three articles concerning privatization of rooms, shared spaces, and small unitization in nursing homes were extracted and analyzed. They were published between 1994 and 2021 in Journal of Architecture and Planning, AIJ Journal of Technology, JAABE, and JAR. The results revealed an evaluation of the privatized rooms mainly from the perspectives of residents' lives and care staffing, the effects and issues of the shared spaces introduced at the same time as private rooms, and the evaluation and issues on subsequent unit‐type floor plans. This study offers significant implications to Asian countries that will have aging and aged populations in the near future by summarizing Japan's experience in dealing with realistic and practical problems over the past 20 years.