Karl Jacob Gummerus (1840–1898), born to an ecclesiastical family, went to the Imperial Alexander University of Finland in Helsinki to study theology, but later moved to the historical-linguistic department in the faculty of arts. In 1863 Tsar Alexander II gave a decree on making Finnish an official language on par with Swedish. Karl Jacob, in spirit of the times, was vigoriously active in developing the "people’s language”. He published his first short story in the Suometar magazine in 1862.

Karl Jacob began his publishing activities with magazines. In 1872 he petitioned the high authority on printing for a publishing permit. The permit was granted on 12 October 1872, which is when Gummerus started its activities as a publisher. Inspired by nationalism, Karl Jacob also became interested in publishing literature. The first book published by Gummerus was Karl Jacob’s own novel Ylhäiset ja Alhaiset ("The Highborn and the Lowly”), which came out in 1870, the same year as Aleksis Kivi’s Seven Brothers. Karl Jacob’s book can be considered the first novel originally published in Finnish, as it had come out as a periodical already in 1864.

In 1877 Karl Jacob founded a printing press in Jyväskylä and became more active as a book publisher.

Fiction was close to Karl Jacob’s heart. During the 1880s Gummerus published, among others, Dostoyevski’s Memoirs from the House of the Dead and Crime and Punishment, as well as Alexandre Dumas’ Three Musketeers.

Karl Jacob believed in more than just financial viability; he carefully considered the contents of the books as well. When it came to non-fiction, he was interested in easily accessible works written in such simple language that an "uneducated, normal, mentally sound person” could understand them.

After the death of Karl Jacob, his widow Gustava continued his work. Gustava was succeeded by Karl Jacob’s nephew Jacob Gummerus, who wanted to secure the future of Gummerus, and changed it into a limited company in 1906.

Popular literature boomed in Finland in the early 1900s. Thus Gummerus gave up publishing sober religious literature, filling its catalogue with a growing range of literary and popular titles, as well as poetry and youth and children’s literature.

At the dawn of Finnish independence Gummerus’ range of publications became ever more diverse. The most significant change in the publishing policy came in the 1920s, when fiction came to account for almost half of all published titles.

In the early 1930s, booksellers acquired a majority of shares in Gummerus, as the Finnish Booksellers’ Association along with private booksellers wanted their own publishing house. During the same decade Gummerus caused a stir while simultaneously raising its literary profile, by publishing a whole range of artistically significant, high-profile books from Finnish writers like Pentti Haanpää, Helvi Hämäläinen, Hella Wuolijoki, and Olavi Paavolainen.

Bookseller Mauno Salojärvi rose to lead Gummerus’ book shop in 1936, and three years later he was chosen as the CEO of the company. Mauno Salojärvi’s business concept was to have a publishing policy stemming from the needs of booksellers. In the early 1940s Salojärvi bought a majority of shares in the company, becoming publisher along with his wife Ruth Salojärvi.

The company’s focus was on translated fiction. Gummerus made bold publishing decisions by setting to print, among others, Vladimir Nabokov’s Lolita and D. H. Lawrence’s Lady Chatterley’s Lover.

The publishing house made the headlines when it published Henry Miller’s Tropic of Cancer  in 1962. Mauno Salojärvi had to explain his publishing decision to a court of law, as according to Finnish law the publication, dissemination, sale, or importation of obscene publications that "offended sexual morality and propriety” was forbidden. The publisher was sentenced to fines.

Pekka Salojärvi, son of Mauno Salojärvi, literally grew up among the printing presses to become a publisher. He was chosen as CEO of Gummerus in 1970. The following year Gummerus published the first instalment of Kalle Päätalo’s impressive Iijoki-series, claimed to be the longest in the world with 26 books.

In the mid 1980s the company changed its name to Gummerus Oy, and was reconstituted into separate subsidiary companies. The company gave up the book shop, and thus its core units were the publishing house and printing house.

After Pekka Salojärvi gave up the position of CEO and joined the board of Gummerus, he was followed as CEO by Risto Lehmusoksa (1985–1994), Ahti Sirkiä (1994–2002), and Ilkka Kylmälä (2002–2011). The company’s present CEO is Mikko Meronen.

The tradition of a family company is still alive, with Pekka Salojärvi’s son Eero Salojärvi joining the board of Gummerus in 1992, and becoming chairman in 2003.