Niiro Tadatsugu served as a bushō during the mid to late Muromachi period. He was a retainer of the Shimazu clan of Satsuma Province and served as the fifth head of the Niiro clan.
Tadatsugu was born as the eldest son of Niiro Tadaharu, the fourth head of the Niiro clan.
In 1458, upon orders of the main branch of the Shimazu clan, he was transferred from Shibushi in Ōsumi Province to Obi in Hyūga Province. Along with Shimazu Hisayasu of the Izaku-Shimazu family based in Kushima in Hyūga, Tadatsugu endeavored to impede the Hyūga-Itō clan.
In 1484, after Tadatsugu became concerned in regard to the expansion of influence of the Izaku family, he requested Shimazu Tadamasa (the eleventh head of the main branch of the Shimazu) to have Hisayasu return to Izaku and Tadamasa consented. Hisayasu, however, resisted while the Hyūga-Itō and the Ōtomo clan of Bungo Province attacked Obi Castle. The main branch of the Shimazu dispatched Hongō Toshihisa and although they protected Tadatsugu, Obi Castle fell to the attackers. In 1485, Tadamasa recaptured Obi Castle. After Hisayasu surrendered, in 1486, Shimazu Tadakado of the Shimazu-Hōshū family was appointed as the lord of the manor of Obi and Tadatsugu was transferred to Sueyoshi and Shibushi.
In 1489, Tadatsugu died and the headship of the clan was inherited by his younger brother, Niiro Tadaaki.