Giddings was first elected to parliament in the 1996 election in the electorate of Lyons but was defeated at the 1998 election. Elected at the age of 23 years she was the youngest woman elected to an Australian Parliament. Until her return to parliament in 2002, she worked for the Tasmanian Premier as a speech writer and media assistant. Giddings was elected one of the five members for the Tasmanian House of AssemblyDivision of Franklin in the 2002 Tasmanian election for the Labor Party. From 2004 to 2006, she was Minister for Economic Development and Minister for the Arts in the Labor government under Paul Lennon. Following the 2006 election, she became Minister for Health and Human Services. Shortly after the election, the State Government decided to proceed with building a replacement for the Royal Hobart Hospital and the significant task of planning the replacement came under Giddings' portfolio. In April 2007, she came under criticism for the poor conditions in the Emergency Department and blamed the federal government for under-funding. On 26 May 2008, Lennon resigned the leadership of the state Labor Party and premiership, and Deputy Premier, David Bartlett was elected party leader and became Premier, while Giddings was elected Deputy Leader and became Deputy Premier, becoming the second woman in Tasmanian history to hold the position. On 23 January 2011, Bartlett stepped down as Premier of Tasmania, and stated that "Lara Giddings will be an outstanding Premier and will have my full support". On 24 January, the State Parliamentary Labor Party unanimously elected Giddings party leader, also becoming Premier. She was the first female Premier of Tasmania until her government's defeat on 15 March 2014. Following her government's defeat, Giddings opted to return to the backbench, the first defeated Premier to do so since Harry Holgate in 1982. Her deputy, Bryan Green, succeeded her as Tasmanian Labor leader. On 14 May 2017, Giddings announced that she would be retiring from politics at the next Tasmanian state election.
In 2011, Giddings stated that pursuit of her political career meant that she may never have children. In September 2017, Giddings announced she was pregnant at the age of 44 with the help of an egg donor. In January 2018, she gave birth to a baby girl with partner Ian Magill.This partnership consequently made her a step-mother of another four children from previous relationships.
Honours
Giddings' official portrait was unveiled at Parliament House in Hobart in 2016. On 16 August 2017, she was granted the use of the title "The Honourable" for life.