His father, a prince of the blood and one-time Buddhist priest, was the head of one of the ōke collateral branches of the Imperial Family created during the early Meiji period.

Educated at the Central Military Preparatory School and the Imperial Japanese Army Academy, he received a commission as a second lieutenant in the IJA 39th Infantry Regiment in 1899.

In 1903, he went to the École Spéciale Militaire de Saint-Cyr at St. Cyr, France, but returned to Japan the following year and served with his regiment as a captain under General Oku Yasukata in the Russo-Japanese War.

[citation needed] In October 1937, he became chief priest (saishu) of the Ise Shrine, upon the death of his half-brother, Prince Kuni Taka.

The prince's arrest caused great consternation among the Japanese, as it opened the possibility that Emperor Shōwa and more senior members of the imperial household might also face prosecution for war crimes.

However, unlike other former members of the Japanese imperial family, the American Occupation authorities (SCAP) purged former Prince Nashimoto allegedly because of his military career, denying him any compensation for the loss of his title and properties.

American bombing raids had already destroyed his Tokyo residence, and he was forced to sell his country villa to pay taxes.