[3] On 24 November 2021, Andersson had been elected to that position but resigned after an announcement by her coalition partner, the Green Party, that they were leaving the government in response to losing the annual budget vote in the Riksdag to the conservative opposition.

[4] After her coalition lost its majority in the 2022 Swedish general election, Andersson announced her intention to resign as prime minister.

[15] Andersson joined the Swedish Social Democratic Youth League (SSU) in 1983 during her first year of secondary school.

[17] After completing her studies in economics, Andersson was employed in at Rosenbad as a political advisor to the then prime minister Göran Persson from 1996 to 1998, and later served as Director of Planning from 1998 to 2004.

[30] On 23 November, it was announced that Andersson had reached an agreement with the Left Party to support her at the upcoming prime ministerial vote.

[31] In September 2024 it emerged that the Social Democrats subsidiary company Kombispel had used unethical sales tactics targeting elderly and confused individuals.

[34] Later in 2024 Andersson unveiled a new party platform which included changes like a stricter immigration policy, new proposed measures to combat crime, and plans to strengthen the welfare state.

[35] Critics argued that the platform made the Social Democrats too similar to the right wing Tidö parties on some issues.

Under Sweden's principles of negative parliamentarism, since a majority was not opposed to Andersson's nomination, this was sufficient to elect her prime minister.

[49][50][51] On 30 November, Andersson and her administration formally assumed office when they met in council with King Carl XVI Gustaf and he announced them.

In her maiden speech as party leader, Andersson said that migrants to Sweden must learn Swedish, work, and graduate high school if they wish to receive welfare.

[56][57] In 2017, as Finance Minister, she said that she regretted the government's decision to grant asylum to 160,000 people during the European migrant crisis in 2015, as she believed that there was not enough housing and employment to integrate them.

[60] On 8 January 2022, it was reported police had arrested a wanted woman who worked as a cleaning assistant at the private residence of Andersson.

[62] On 2 June, the Sweden Democrats (SD) put forward a confidence vote against Minister for Justice Morgan Johansson, alleging that he did not properly tackle gang violence and the ongoing recruitment of people into them.

"[63] In August, a month before the 2022 Swedish general election, Andersson confirmed that she had confronted Christian Democrats (KD) leader Ebba Busch at Expressen about a supposed theft of campaign posters outside the Prime Minister's residence.

[68] Following the 2022 Russian invasion of Ukraine in February, Sweden and the Social Democrats began to reevaluate their traditional position of neutrality.

[72] She welcomed the deal agreed by European Union leaders to ban more than 90 percent of Russian oil imports by the end of the year.

[77] On 30 June, Turkish President Recep Tayyip Erdoğan said that Sweden had made a promise to extradite to Turkey what he characterised as "73 terrorists".

Andersson refused to deny Turkey's claim that Sweden had promised to deport Turkish political refugees and opponents wanted by Erdoğan's government.

[78] Ahead of the 2022 Swedish general election, then Minister for Integration Anders Ygeman presented new efforts to combat segregation, saying that he wants to introduce a 50 percent-maximum cap of how many people with non-Nordic ethnic background can live in a certain area.

[82] When interviewed by the newspaper Expressen after the election, and the Kristersson Cabinet had been formed, Andersson said she was happy with the new government's harsh policies on migration and asylum and reiterated that it was her predecessor, former Prime Minister Stefan Löfven, who was responsible for the real paradigm shift regarding migration after the 2015 refugee crisis.

[83] For this shift in her stance on migration she was criticized by editors in left leaning newspapers[84] Shortly after she took office in 2021, Andersson said in an interview with Dagens Nyheter that she believes more criminals who lack Swedish citizenship should be deported.