Itō was born in Tanabe Domain, in what is now part of Maizuru city, Kyoto prefecture.

A gifted child with a flair for mathematics, he was sent by the domain leaders to Edo, where he studied rangaku under noted military theorist Ōmura Masujirō.

He served in the fledgling Imperial Japanese Navy as captain of the frigate Kasuga in 1871, with the rank of lieutenant commander.

Itō was promoted to rear admiral on 6 June 1886 and subsequently served in various staff capacities in charge of warship procurement though 1889.

On 20 August 1895, Itō was ennobled with the title of baron (danshaku) under the kazoku peerage system.