To some extent she said in 1939 that they did not believe "all the rumours".,[2] but following the Nazi occupation of Czechoslovakia in 1939, the Webers were able to get their oldest son, Hanuš, safely to Sweden on a "Kindertransport" before they were confined to Prague's Jewish Ghetto.

Ilse Weber worked as a night nurse in the camp's children's infirmary, doing everything she could for the young patients without the aid of medicine (which was forbidden to Jewish prisoners).

She wrote around 60 poems during her imprisonment and set many of them to music, employing deceptively simple tunes and imagery to describe the horror of her surroundings.

Her songs include "Lullaby," "I Wandered Through Theresienstadt," "The Lidice Sheep," "Wiegala," "And the Rain Falls," and "Avowal of Belief.

"[3] When her husband was deported to Auschwitz in October 1944, Ilse Weber volunteered to join him with their son Tommy because she didn't want to break up the family.

[5] Years later, on April 15, 2018, one of her patients from Theresienstadt, Aviva Bar-On sang, without a written trace and only from memory, one of Ilse Weber's songs during a concert in Jerusalem.

Her songs have been frequently recorded, particularly "Lullaby," most recently by mezzo-soprano Anne Sofie von Otter and Christian Gerhaher (2007).

Weber's surviving son Hanuš participated in a cultural program commemorating his mother's work in Berlin on 22 May 2008.