Jinbō Nagazumi served as a bushō during the Sengoku and Azuchi-Momoyama periods.
Around 1568, Nagazumi advocated for alliances with the Kai-Takeda clan and the Kaga Ikkō-ikki, while his father, Nagamoto, sought to maintain their subservient relationship with the Uesugi clan. This led to divisions within the Jinbō family with Nagazumi and those in the faction opposed to the Uesugi on one side and Nagamoto and senior retainers such as Kojima Motoshige on the other. In the tenth month of 1569, Uesugi Kenshin of Echigo Province intervened, subduing Nagazumi and those in the faction opposed to the Uesugi. On 11/16 of Tenshō 5 (1577), Kenshin granted the village of Hosoya in the Suzu District of Noto Province and the allocation of 89 kan, 457 mon from Nagamoto to Iida Yosōzaemon. After losing the internal conflict, Nagazumi resided with the Noto-Hatakeyama clan and appeared to have had landholding, although another Jinbō family was associated with the Noto-Hatakeyama so this may have been a different individual. Noto, however, was also under the control of the Uesugi, so Nagazumi appeared to have then gone to Kyōto and served Oda Nobunaga.
In 1578, the sudden death of Uesugi Kenshin provided an opportunity for Nobunaga so he assigned Sassa Nagaaki and other troops to Nagazumi and had him serve as the vanguard of the Oda army to invade Etchū via Hida Province. After allying with kokujin, or provincial landowners, including Saitō Nobutoshi, Kotani Rokuemon and Ninomiya Nagatsune, attacked Masuyama Castle, and garnered control of the southwest portion of Etchū. In the ninth month, Saitō Toshiharu led soldiers from Nōbi as reinforcements and, at the Battle of Tsukiokano, achieved a major victory over the Uesugi and Shiina forces. The army of reinforcements including the Saitō forces soon returned to their home province, while Nagazumi proceeded north from Tsuge Castle to to recapture Toyama Castle which was associated with the Jinbō clan. Next, he continued active military operations, marching east to attack Shinjō and Matsukura castles. In 1581, after Sassa Narimasa entered Etchū, Nagazumi came under his command.
In the third month of 1582, Nagazumi was captured during a surprise attack at Toyama Castle by former retainers including Kojima Motoshige and Karōdo Chikahiro. Before long, he was rescued by a counterattack mounted by the Oda army but, owing to this event, Nagazumi lost his standing and was ousted. Therefter, Kikuchi Uemon Nyūdō, a kunishū, or provincial landowner, who was formerly under the command of Nagazumi, made a request to Shibata Katsuie, a senior retainer of Oda Nobunaga, to mediate conditions on behalf of Nagazumi but was refused, and, the following year, went to the Ise Shrine to pray for his return to Etchū. Nagazumi’s whereabouts thereafter are unknown.