[1] Leissner was born on 21 January 1956 in Gothenburg, Sweden, the son of Pehr Leissner, a doctor, and his wife Ulla (née Hallberg), a sociologist.

[2] She completed studies in Gothenburg and at Uppsala University (international economics) from 1975 to 1980.

[2] Leissner was chairman of the Swedish Committee for Afghanistan from 1991 to 1995 and the Women Can Foundation (Stiftelsen Kvinnor kan) from 1993 to 1995.

On 5 October 2017, she took office as Stockholm-based ambassador of Sweden to Benin.

[4] From 1982 to 1996, Leissner was in a domestic partnership with Hans Holmgren (1982–1996), the son of civil engineer Karl Olof Holmgren and Ingrid (née Stener).