[6] NTT was also one of the world's largest companies by market capitalization from its initial public offering in 1987 until the Japanese economic bubble burst in 1991.

[8] The purpose of the company defined by the law is to own all the shares issued by Nippon Telegraph and Telephone East Corporation [ja] (NTT East) and Nippon Telegraph and Telephone West Corporation [ja] (NTT West) and to ensure proper and stable provision of telecommunications services all over Japan including remote rural areas by these companies as well as to conduct research relating to the telecommunications technologies that will form the foundation for telecommunications.

Established as a state monopoly in August 1952 to take over the Japanese telecommunications system operated by AT&T during the Occupation of Japan,[citation needed] Nippon Telegraph and Telephone Public Corporation (日本電信電話公社, Nippon Denshin Denwa Kōsha, shortened into Den-Den Kōsha (電電公社)) was privatized in 1985 to encourage competition in the country's telecom market, making Japan the first Asian country and only the second in the world (after the United States) to deregulate its telecom market.

The proceeds will be used for environmentally friendly projects (renewable energy, energy-efficient broadband infrastructure, etc.).

[9] In 2023, the World Intellectual Property Organization (WIPO)’s Annual PCT Review ranked Nippon Telegraph and Telephone's number of patent applications published under the PCT System as 10th in the world, with 1,760 patent applications being published during 2023.