The holdings of the National Diet Library are collected through the legal deposit system, purchase, exchange and donation. These collections are separately held in the Tokyo Main Library, the Kansai-kan and the International Library of Children's Literature. The holdings of the Tokyo Main Library are the following:

• Japanese and Western books
• Japanese periodicals
• Annual periodicals and some monograph series in Western languages
• Japanese and Western newspapers
• Materials stored in the special materials rooms (including digital publications such as electronic journals and CD-ROMs)

The following materials have been transferred to the Kansai-kan:

• Western periodicals (excluding annual periodicals and some monograph series)
• Asian materials (books, periodicals and newspapers in Asian languages)
• Some science and technology materials (technical reports, foreign papers of academic societies and associations, Japanese and foreign standards, foreign patents, foreign doctoral dissertations, conference proceedings in Western languages)
• Scientific research reports under grants from the Ministry of Education, Culture, Sports, Science and Technology
• Japanese Doctoral dissertations
• Tape recorded books

• Collections of the Kansai-kan
• International Library of Children's Literature