Goldie was elected to the Scottish Parliament in the 1999 election as a regional member for the West of Scotland electoral region. She has retained this seat in the 2003, 2007 and 2011 elections. She became leader of the Scottish Conservatives in 2005 until standing down in 2011. In addition to her appearance on the regional list ballots, she also stood as a candidate in the West Renfrewshire constituency for the Scottish Parliament in 1999, 2003 and 2007. While increasing the Conservative share of the vote each time, she has yet to be elected although raised her position from third to second place in 2007 with a reduced Labour majority. The constituency was abolished at the 2011 election, with Goldie unsuccessfully contending the new Renfrewshire North and West constituency.
Leader of the Scottish Conservatives
On 31 October 2005, Goldie became acting leader after David McLetchie resigned as leader of the Scottish Conservatives following adverse publicity created by the publishing of details of expenses he claimed for taxi journeys. Goldie put herself forward as a leadership candidate on 2 November 2005—a joint nomination with Murdo Fraser as her proposed deputy. Their nomination was unopposed and Goldie was appointed leader on 8 November 2005, the first woman to lead the Scottish Conservative Party. In her maiden speech as leader, she promised to act against "disloyalty and disobedience" in the party and in a reference to Margaret Thatcher she said, "I think you may take it matron's handbag will be in hyper-action. There could be worse precedents to follow". At her first party conference in March 2006, Goldie set out her plans to make the Scottish Conservatives the "principal party of opposition in Scotland". However, her second conference as party leader was overshadowed by a leaked memo by David Mundell, the only Scottish Conservative MP in the House of Commons, and Shadow Secretary of State for Scotland, in which he criticised Goldie's leadership. Goldie won praise for her leadership of the party into the 2007 Scottish Parliament election and personally as a skilled debater, and was labelled a "much-liked public figure". From February 2009 onwards, she was given monthly attendance rights to participate in the Official Opposition Shadow Cabinet in Westminster. On 9 May 2011, Goldie stated her intention to resign as leader of the Scottish Conservatives, citing her party's disappointing election result; she stood down on 4 November, following the election of Ruth Davidson as her successor.
Goldie was created a life peer on 3 October 2013, taking the title Baroness Goldie, of Bishopton in the County of Renfrewshire. In June 2016, Goldie was appointed a Baroness-in-Waiting in the Royal Household, acting as a whip in the UK Government. In July 2019, she was promoted to Minister of State for Defence.