1901 Hoshio Mitsunaga establishes Japan Advertising Ltd. and Telegraphic Service Co.
1906 Telegraphic Service Co. becomes Japan Telegraphic Communication Co., Ltd.
1907 Japan Advertising Ltd. merges with Japan Telegraphic Communication Co., Ltd. and starts to engage in communication and advertising operations.
1936 Japan Telegraphic Communication Co., Ltd. relinquishes its news services department to Domei News Agency and re-launches itself as a specialized advertising agency.
1940 Shinzo Mitsunaga becomes the second President.
1943 The Company acquires 16 companies in a move to augment its advertising agency business. Operational bases are established in Tokyo, Osaka, Nagoya and Kyushu.
1945 Sekizo Ueda becomes the third President.
1947 Hideo Yoshida becomes the fourth President.
1948 Creation of the Dentsu Advertising Awards.
1949 Creation of the Dentsu Advertising Essay Contest for Students.
1951 Dentsu establishes the Radio Division at its Head Office and local offices. Commercial radio broadcasting begins in Japan.
1953 Dentsu creates the Radio and Television Division at its Head Office and local offices. Commercial television broadcasting begins.
1955 Dentsu Advertising Ltd. becomes the new company name.
1963 Tsuneji Hibino becomes the fifth President.
1967 Completion of Tsukiji Head Office Building.
1973 Yoshichika Nakahata becomes the sixth President.
1974 Advertising Age ranks Dentsu No. 1 advertising agency worldwide in terms of (calendar 1973) billings.
1977 Hideharu Tamaru becomes the seventh President.
1981 The company formerly known as JIMA Dentsu Advertising, Ltd. and U.S. partner Young & Rubicam's Japanese affiliate establish Dentsu Young & Rubicam as a joint venture in Tokyo.
1984 Dentsu and U.S.-based Young & Rubicam jointly establish DYR, an international service network.
1985 Gohei Kogure becomes the eighth President.
1988 Advertising Age names Dentsu the 1987 "International Agency of the Year."
1989 Fiscal 1989 billings exceed 1 trillion yen.
1993 Gohei Kogure becomes the first Chairman. Yutaka Narita becomes the ninth President.
1995 Dentsu establishes five domestic regional subsidiaries.
1996 Japan-China Advertising Education Exchange Project commences. Dentsu Tec Inc. is established.
2000 Dentsu makes an equity investment in the Bcom3 Group. Information Services International-Dentsu, Ltd. lists its shares on the First Section of Tokyo Stock Exchange.
2001 Dentsu lists its shares on the First Section of Tokyo Stock Exchange. Dentsu commemorates its 100th anniversary.
2002 Yutaka Narita becomes the second Chairman. Tateo Mataki becomes the 10th President. The Bcom3 Group merges with Publicis Groupe S.A. Dentsu acquires a 15% stake in the newly formed group. Dentsu's new Shiodome Head Office Building opens in November.
2003 Dentsu East Japan Inc., Ad Dentsu Tokyo Inc. and Dentsu Tohoku Inc. merge, with Dentsu East Japan as the surviving company.
 Geneon Entertainment Inc. and Geneon Entertainment (USA) Inc. are converted to subsidiaries.
2004 Tateo Mataki becomes the President & CEO.
 Dentsu Group initiates the UNESCO World Terakoya Movement "kururimpa" project.
2005 Dentsu Group obtains BS7799 certification and Information Security Management Systems (ISMS) certification.
 All of Dentsu's domestic branch offices receive ISO 14001:2004 certification.
2006 Dentsu Tec is converted to a wholly-owned subsidiary, and its shares are delisted.
2007 Dentsu Group achieves consolidated billings (net sales) of 2 trillion yen.
Tateo Mataki becomes the third Chairman. Tatsuyoshi Takashima becomes the eleventh President.
2008 Dentsu establishes an internal committee for the deliberation of environment-related strategies.
Dentsu receives "Eco-First Company" certification.
2009 Dentsu announces the new Dentsu Group corporate philosophy: "Good Innovation."
Dentsu introduces the "Director, Member of the Board & Executive Officer" management system.
cyber communications inc. becomes a wholly-owned subsidiary.
Dentsu Announces New Medium-Term Management Plan "Dentsu Innovation 2013".
2010 Dentsu establishes Dentsu Digital Holdings.
 Dentsu establishes Dentsu Network West.
2011 Tatsuyoshi Takashima becomes the fourth Chairman. Tadashi Ishii becomes the twelfth President & CEO.
2012 Dentsu establishes the Dentsu Network, an umbrella organization of the Company's agencies outside Japan. Dentsu Network West is absorbed into the Dentsu Network.
2013 Dentsu acquires Aegis Group plc and establishes a new global operating unit, Dentsu Aegis Network Ltd., in London.
2014 Dentsu Appointed as Marketing Agency by the Tokyo Organising Committee of the Olympic and Paralympic Games.
2017 Toshihiro Yamamoto becomes the thirteenth President & CEO.
2020 Transitioned to a new holding company structure, and Toshihiro Yamamoto became the first appointed to Dentsu Group Inc.
Hiroshi Igarashi was appointed the 14th President of Dentsu Inc.