Marwick was born on 5 November 1953 in Cowdenbeath and was brought up in Fife, one of seven siblings. She worked as Public Affairs Officer for Shelter Scotland, a charity for homeless people, from 1992 to 1999. Her niece is Natalie McGarry (the former MP for Glasgow East).

In the 1999 Scottish Parliamentary election, Marwick was elected as a member for the Mid Scotland and Fife region. She served on the SNP opposition frontbench team as Deputy Business Manager 1999–2000, Shadow Minister for Local Government 2004, Business Manager and Chief Whip 2004–2005 and Shadow Minister for Housing 2005–2007. Marwick has also served as a member of the Scottish Parliament’s Standards, Justice and Home Affairs, Equal Opportunities, Local Government and Communities committees and as convenor of the Waverly Railway (Scotland) Bill committee from 2004–2006.

At the 2003 Scottish Parliamentary election she contested the Central Fife seat and, although she narrowly failed to win the seat, she was re-elected to serve as a member for Mid Scotland and Fife. Marwick contested Central Fife again in 2007 and was elected as the constituencies MSP after defeating the Labour incumbent, Christine May, with a majority of 1,166 votes.

Following the 2007 election Marwick was appointed as the SNP’s representative on the Scottish Parliamentary Corporate Body, and oversaw parliamentary access and information issues.

In the 2011 election, Marwick was elected for the Mid Fife and Glenrothes constituency, essentially a redrawing of her old Central Fife seat. On 11 May 2011, when Parliament reconvened, Marwick was elected to serve as the 4th Presiding Officer of the Scottish Parliament, having won support from the majority of members in the second round of voting. She became the first woman and second SNP member to serve in the position. In October 2012, Marwick accepted a nomination to join the Privy Council, meaning that she is styled the Rt Hon. Tricia Marwick MSP. Each of the previous Presiding Officers were also appointed to the Privy Council.

On 29 May 2015, it was announced that Marwick would step down as Presiding Officer after the 2016 election.

In June 2016 Marwick revealed that she had turned down an offer to put her name forward for an honour from the Queen.

Marwick was announced as the new chair for the NHS Fife board in November 2016, replacing Allan Burns who resigned from the post in August 2016. Her appointment as chair will run from 1 January 2017 until 31 December 2020.