Nagahiro"s mother was a woman of humble origins named Chisa. She had attracted Shigehide"s attention with her "sturdy build and great love of sake." Much like his mother, Nagahiro was also well-built. He was close in age to Shimazu Nariakira, and the two had a brotherly relationship.
After Commodore Perry"s arrival, Nagahiro (like his close relative, Shimazu Nariakira) was a proponent of opening the country.
He greatly encouraged learning amongst his retainers, and sent them to the best schools of Edo, Osaka, and Nagasaki to absorb the Western knowledge and technical expertise which was entering the country at the time. He himself also engaged in similar efforts, listening to the anatomy lectures of Philipp Franz von Siebold in 1859.
In the Boshin War, his forces took part in the campaign against the domains of the Tōhoku region. Nagahiro held the title of Mino no Kami (美濃守) as well as junior 2nd court rank (juni"i 従二位).
In the Meiji era, he was created kōshaku (侯爵.
Marquess) in the new peerage system.