Tewosret was married to Seti II and mother of Seti-Merenptah who was the heir-apparent but who died before he became king. She was also stepmother to Siptah, a son of a younger queen of Seti II. Siptah succeeded his father and when he too died, Tewosret as his stepmother declared herself King. She used a full royal titulary, just as Hatshepsut had done ca 300 years earlier. Her reign was short, only a couple of years. The times were unruly, with hardships for the people, and she and her close advisor, the Chancellor Bay, was put to blame for these circumstances.

She had her tomb built and was put there at her death. Later, she was ousted from it by King Setnakhte, the first ruler od the 20th Dynasty. When she died, the 19th dynasty ended. She is buried in Tomb KV14 Valley of the Kings.