Tajima was born in Araki, an area which was then Wan Village, in the westernmost part of Kikaijima Island. Since February 2002, she has 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 has nine children (seven sons and two daughters). As of September 2011, Tajima had 28 grandchildren, 56 great-grandchildren and 35 great-great-grandchildren. As of September 2015, she had over 140 descendants, including great-great-great-grandchildren. As of September 2017, she had around 160 descendants.
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. On 15 September 2017, upon the death of the 117-year-old Jamaican Violet Brown, Tajima became the oldest living person in the world—and the last surviving person born in the 19th century. On 10 February 2018 it was announced that she had surpassed the age of Violet Brown and become the fifth-oldest person in history whose age has been validated.