However, she faces a tough job from the outset, with opposition parties on the right saying they’ll reject the government’s 2022 budget later on Wednesday. The Centre party, which backed her for the job of prime minister, says it will not support a finance package from a government “moving far to the left”.
As well as the uphill task of getting a budget passed, Ms Andersson faces other big challenges as she takes on the role.
Although Sweden has a relatively low rate of Covid-19 infection, there are concerns that infections will peak next month.
The government announced on Wednesday that third Covid vaccinations would be rolled out to everyone over 18, and that vaccination passes would be required for any public gathering involving over 100 people from 1 December.