Seiko Group is the corporate parent of various entities that design, manufacture, and market Seiko brand watches, along with many other products.

The company began in 1881 when Kintarō Hattori opened the “K Hattori” watch and jewelry shop in the Ginza area of Tokyo Japan. The next year, he founded a clock manufacturing operation called Seikosha. K. Hattori & Co, Ltd. is founded in 1917 as a parent company for Seikosha. In 1937, the watch production operations of Hattori/Seikosha is split off to a new company, Daini Seikosha, Ltd. (“the second Seikosha”).

• See also Suwa Seikosha calibres and Daini Seikosha calibres

Beginning in 1959, Seiko maintained two competitive operations to design and manufacture watches, Daini Seikosha and Suwa Seikosha. This system led to the creation of the Grand Seiko and King Seiko lines, making Seiko a competitor in the high-end watch industry in the 1960's and beyond.

The split originated outside the Hattori operation. In 1942, Hisao Yamazaki founded Daiwa Kogyo in Suwa, Nagano, and Seiko established a joint-venture plant there the following year. In 1959, the Seikosha and Daiwa operations in Suwa merged to form Suwa Seikosha, a center of high-end watchmaking for Seiko focused on men's watches. This would be the originator of the Grand Seiko line, with the first model produced in 1960.

Meanwhile, Daini Seikosha continued as a center of watch manufacturing for Hattori. They funneled their ambitions into an alternate high-end line, introducing the first King Seiko in 1961. In 1967, Daini's 44GS entered the Grand Seiko lineup, setting the “Grand Seiko Style” for the company's future.

Suwa continued to innovate, introducing an automatic Grand Seiko in 1966 and a "Hi-Beat" automatic in 1968. The two operations competed into the 1970's, with Suwa producing a King Seiko in 1969 and Daini contributing one of the finest watches of the time in 1970.

But the industry had changed, with quartz watches rapidly becoming Seiko's core asset and an expanding electronics business, Epson Corporation, on the rise. In 1983 and 1985, Daini Seikosha became Seiko Instruments & Electronics (SII) and Suwa Seikosha and Epson merged to become Seiko Epson Corporation. A separate watch movement company, Time Module (TMI) was formed by all Seiko businesses in 1987.

Hattori became simply Seiko Corporation in 1990 and was renamed Seiko Holdings in 2007. In 2009, Seiko Instruments became a wholly-owned subsidiary of Seiko Holdings, bringing most of the company's mechanical watch-related activities under one roof. Daini Seikosha's high-end watch manufacturing continues at Shizukuishi Watch Studio, producers of Grand Seiko, Credor, and other high-end timepieces for the Seiko brand.

Seiko Epson continues as an independent company, operating the Orient watch company and producing many of the mass-market quartz watches for Seiko. Although there are common shareholders, Seiko Epson is fully independent of Seiko Holdings.

• Deconstructing Seiko