Born Auguste van Pels on September 29, 1900, in Buer near Osnabrück, Germany, she adopted the name Petronella van Daan upon marrying Hermann van Pels on December 5, 1925, and gained Dutch citizenship. The couple had a son, Peter, born November 1926. Fleeing Nazi persecution, they moved to Amsterdam in 1937. There, Hermann partnered with Otto Frank, and the families lived nearby. After unsuccessful attempts to emigrate to the United States, the Van Pels family entered hiding with the Franks in the Secret Annex on July 13, 1942.

During concealment, Petronella displayed a talkative, flirtatious nature and frequently quarreled, especially with her husband. She engaged in political discussions while exhibiting fatalistic, egotistical, stingy, and disagreeable traits. Her materialism surfaced through actions like preserving a fur coat and prioritizing possessions. Interactions with fellow occupants remained tense; she openly criticized Anne Frank and others, complaining about circumstances and provoking conflicts. Despite this, flashes of humor emerged. She maintained closeness with Peter while clashing persistently with Hermann.

Following the August 4, 1944, raid on the Annex, Petronella was detained and sent to Westerbork transit camp. She was deported to Auschwitz-Birkenau and later forced on a death march during the camp’s evacuation. She collapsed and died en route between Raguhn (a Buchenwald subcamp) and Theresienstadt. The exact date and conditions of her death are undocumented.