She joined the Italian Communist Party and became the leader of the Milan office, after a period as city councillor.
She retired from politics when was indicted for political corruption during the inquiry called Mani pulite, until her acquittal in 1996. She subsequently joined the Democratic Party of the Left and in 1999, she became head of the women's group of the Democrats of the Left.
Since 23 May 2007, she has been a member of the National Committee for the Democratic Party. On 7 May 2017, Pollastrini was appointed Vice President of the Democratic Party, representing the left-wing of the party.