Naoe Kagetsuna served as a bushō during the Sengoku and Azuchi-Momoyama periods.  He was a retainer of the Nagao clan (Uesugi clan), the deputy military governor and sengoku daimyō of Echigo Province.  Kagetsuna served as the lord of Yoita Castle in the Santō District.

Kagetsuna was a veteran, serving three generations of the Nagao family including Nagao Tamekage, Nagao Harukage, and Nagao Kagetora (later known as Uesugi Kenshin).  He worked as a magistrate handling both domestic and diplomatic affairs.  Also active in the military arena, he was counted among the Seven Generals of the Uesugi.

The Naoe were originally members of the Miwa Clan or else descended from Fujiwara no Maro, a noble from the Nara period.  There are many uncertainties with respect to their genealogical records.  Historical materials allow for the corroboration of facts from the era of Kagetsuna’s father, Naoe Chikatsuna.

Kagetsuna was born as the son of Naoe Chikatsuna around 1509.

The Naoe clan were servants of the Inuma clan who were, in turn, retainers of the Uesugi, the deputy military governors of Echigo.  In 1514, Nagao Tamekage decimated the Inuma, after which the Naoe became the lords of the former base of the Inuma at Motoyoita Castle (later known as Yoita Castle).

Date Tanemune was the fourteenth head of the Date family and a sengoku daimyō of Mutsu Province.  Tanemune sought to further expand his domain by sending his third son, Tokimunemaru (later known as Date Sanemoto), for adoption by Uesugi Sadazane, the military governor of Echigo, to become the designated heir to the Uesugi.  The Date had connections to the Uesugi and to Echigo.  Tokimunemaru’s grandmother on his father’s side hailed from the Uesugi, while his mother was the younger sister of Nakajō Fujisuke, lord of Tossaka Castle in Echigo.

The willingness of Sadazane to entertain the proposal from Tanemune to adopt Tokimunemaru triggered fierce opposition among members of the Uesugi who understood this would make the Uesugi subservient to the Date.  During the formation of factions for and against the proposal, Kagetsuna aligned with Nakajō Fujisuke and a gōzoku, or wealthy family, known as the Tairako clan, to advocate for the adoption.  Nagao Tamekage, the prior deputy military governor who continued to wield influence in Echigo, supported the plan to bind the families through the adoption, but, after learning of Tanemune’s intentions to intervene militarily, made clear his opposition to the plan.  As a result, the Naoe and Nagao clans stood on opposite sides of the adoption issue, creating a fissure between them.  Similar divisions within the Date clan over this issue then escalated into the Tenbun Conflict.

In 1542, Kagetsuna served as a messenger to the Date family for the welcoming of Tokimunemaru.  However, after the opposition factions in both the Date and Uesugi families prevailed, the adoption plans fell through.

In 1543, Nagao Kagetora entered Tachio Castle as a proxy for his older brother, Harukage, who was of frail health.

In 1546, Kagetora attacked the Kuroda clan at Kurotaki Castle in the village of Yahiko who were hostile toward his older brother, Harukage.  This event served as a catalyst for a movement to back Kagetora as the deputy military governor in place of the frail Harukage.  Kagetsuna was one of the individuals promoting this initiative.  The relationship between Kagetsuna and Kagetora was established around the time that Kagetora was operating in the environs of Tachio.

In 1547, when a dispute in the Nagao clan erupted between Kagetora and his older brother, Harukage, Kagetsuna joined Nakajō Fukisuke and Honjō Saneyori to support Kagetora.

In 1556, a hereditary retainer named Ōkuma Tomohide was ousted by Nakajō Fujisuke and others during the disturbance in the Uesugi family accompanying Kagetora’s decision to enter the priesthood.  This provided an opportunity for Kagetsuna and Saneyori to manage many affairs of the clan in their capacity as magistrates.  In 1559, when  Kagetora traveled to Kyōto a second time, Kagetsuna, together with Kanamari Chikatsuna, handled arrangements with the Imperial Court and the bakufu.  In 1560, when Konoe Sanehisa, the former kanpaku, or Chief Advisor to the Emperor, visited Echigo, Kagetsuna was in charge of hosting his visit.  That same year, when Kagetora was on deployment to the Kantō in an expedition to subdue Hōjō Ujiyasu of Sagami Province, Kagetsuna and Yoshie Kagesuke remained behind to guard Kasugayama Castle.  In 1561, at the Fourth Battle of Kawanakajima, Kagetsuna managed the transport of military provisions, contributing to the defeat of the army of Takeda Yoshinobu.  In 1562, he was conferred the title of Yamato-no-kami, or Governor of Yamato, and changed his name to Masatsuna.  In 1564, he received one of the characters from the name of Kagetora (Kenshin’s former name) and adopted the name of Kagetsuna.

According to records of military service of the Uesugi family from 1575, Kagetsuna was assigned the services of 305 personnel, indicating a high-level of responsibility among the group of hatamoto serving under the direct command of their lord.  Beginning in 1576, Kagetsuna served in numerous battles for Kenshin such as to defend Sekidōsan Castle during an expedition to Noto Province.  On 3/5 of Tenshō 5 (1577), he died of illness at the age of sixty-nine.  His grave was built at the Tokushō Temple in Yoita in Echigo.

Kagetsuna did not have any sons, so he was succeeded by his adopted son-in-law, Naoe Nobutsuna, who originated from the Nagao clan.  In 1581, Nobutsuna was murdered by Mōri Hidehiro upon orders of Uesugi Kagekatsu who sought to suppress the high-ranking Naoe family.  A close associate of Kagekatsu named Higuchi Kangetsugu (later Naoe Kanetsugu) then wed Nobutsuna’s widow and inherited the Naoe family.