Gertrud Siemsen, known as Gertie, graduated from school in Frankfurt am Main in 1927. She then became a shorthand typist. In 1928 she began studying economics, history, psychology, and philosophy in Frankfurt. During her studies, she worked as an assistant to professors such as Theodor W. Adorno. She gained a PhD in 1933.
In 1941 Gertie Siemsen moved to Berlin and worked for an advisory body on metal processing. At the same time, her longstanding partner Harald Poelchau began helping persecuted Jews. She was aware of his aid activities and provided practical support. She obtained food ration coupons, money, accommodation, and work for the Latte family, who were living in hiding. Konrad Latte spent several nights in her home.
In March 1945, Gertie Siemsen had Harald Poelchau’s daughter. She experienced the end of the war in Berlin with her baby. She began working in Berlin’s justice system in 1946, becoming a prison director and placed in charge of Tiergarten women’s prison from 1953.
The Israeli Holocaust memorial center Yad Vashem honored her posthumously as Righteous Among the Nations in 2002.