Tajima was born in Araki, an area which was then Wan Village, in the westernmost part of Kikaijima Island. From February 2002 until her death, she resided in a nursing home named "Kikaien" (喜界園) in Kikai, Kagoshima.
Her husband, Tominishi Tajima (田島 富二子), died in 1991 at the age of 95 according to some sources, or possibly 1992 or 1993 according to others. She had nine children (seven sons and two daughters). In September 2017 she was reported as having around 160 descendants, including great-great-great-grandchildren.
Tajima became the oldest living person in Japan on 27 September 2015, upon the death of a 115-year-old anonymous woman who was living in Tokyo. Violet Brown died on 15 September 2017 in Jamaica (UTC-5). In Japan, where Tajima lived, the date was already 16 September 2017 (JST), and Tajima became the oldest living person in the world—and the last surviving person born in the 19th century. On 10 April 2018, Nabi Tajima became the world's third oldest person ever due to surpassing the final age of Lucy Hannah. Others have claimed to be older, but none of these claims have been sufficiently validated.