Its first major publication was Natsume Sōseki's novel Kokoro, which appeared as a book in 1914 after being serialized in the Asahi Shimbun.

Iwanami has since become known for scholarly publications, editions of classical Japanese literature, dictionaries, and high-quality paperbacks.

In its early years, the company published authors such as Natsume Sōseki, Kurata Hyakuzō and Abe Jiro.

Shortly before his death in 1946, he founded the newspaper Sekai, which had a great influence in post-war Japanese intellectual circles.

[4] In 1955, the company released its Japanese language dictionary, Kōjien, which is highly regarded today and sold more than eleven million copies in 2007.