[6] At the 1992 general election, Eagle stood as the Labour Party candidate in Crosby, coming second with 25.7% of the vote behind the incumbent Conservative MP Malcolm Thornton.

[7][8][9] Prior to the 1997 general election, Eagle was selected through an all-women shortlist to stand as the Labour candidate in Liverpool Garston.

[13] She became a member of the Public Accounts Committee and in 1999 she was appointed the Parliamentary Private Secretary to the Minister of State at the Department of Health, John Hutton.

[14] Eagle was re-elected as MP for Liverpool Garston at the 2001 general election with an increased vote share of 61.4% and a decreased majority of 12,494.

[15] Eagle was promoted to the Tony Blair government following the 2001 general election as a Parliamentary Under-Secretary of State at the Department for Work and Pensions.

In September 2008, she was nominated for Stonewall Politician of the Year for her work to support equality for lesbian, gay and bisexual people.

[24][25] Eagle was appointed Shadow Secretary of State for Defence in September 2015 by newly elected Labour leader Jeremy Corbyn.

[28] Tasked with leading Labour's defence review, she said she would not rule out the possibility of it recommending unilateral disarmament.

[29] In January 2016, Eagle was moved to the position of Shadow Secretary of State for Culture, Media and Sport.

[31] She supported Owen Smith in the failed attempt to replace Jeremy Corbyn in the 2016 Labour leadership election.

[39] In November 2024, Eagle voted in favour of the Terminally Ill Adults (End of Life) Bill, which proposes to legalise assisted suicide.