On 4 May 2007 Combet announced his intention to run for the safe Labor seat of Charlton in Newcastle, New South Wales.
The sitting member for Charlton, Kelly Hoare, expressed anger at losing preselection for her seat, and for a time considered running as an independent.

Combet stood down as ACTU Secretary to campaign full-time in Charlton in the lead up to the federal election.
On 14 June 2007 Jeff Lawrence, National Secretary of the Liquor, Hospitality and Miscellaneous Union (LHMU) was elected unopposed as the next Secretary of the ACTU.

Combet was elected as the new member for Charlton on 24 November 2007 as part of the ALP's victory in the 2007 Australian federal election, achieving a two party preferred swing of 4.47 per cent, winning 62.87 per cent of the two party vote.
Following the election, Prime Minister Kevin Rudd appointed Combet as Parliamentary Secretary for Defence Procurement in the First Rudd Ministry.
He was sworn in on 3 December 2007.
In February 2009, Combet was appointed Parliamentary Secretary for Climate Change, with a focus on emissions trading, to assist Climate Change Minister Senator Penny Wong.

As a result of the resignation of Defence Minister Joel Fitzgibbon and the subsequent ministerial reshuffle, Combet was promoted to the ministry on 6 June 2009, as Minister for Defence Personnel, Materiel and Science and Minister Assisting the Minister for Climate Change.
Combet's portfolio was amended into April 2010 to Minister Assisting the Minister for Climate Change and Energy Efficiency and Minister for Defence Materiel and Science and to help him focus on the Government's energy efficiency programs, he axed part of this scheme—Home Insulation Program (HIP) in late April due to the safety risks and the blow-out in funding.

Combet was re-elected to Charlton at the 2010 federal election, suffering a post-redistribution two party swing of 0.24 per cent, winning 62.67 per cent of the two party vote.
After Labor was returned to government in this election, Combet entered Cabinet, succeeding Wong as Minister for Climate Change and Energy Efficiency.
Following the passage of the government's Clean Energy Bill, the portfolio of Industry and Innovation was added to Combet's responsibilities.
Combet had decided to step down over health concerns prior to Prime Minister Gillard's defeat in a leadership spill on 26 June 2013, but brought this decision forward and announced he would step down as minister and not contest his seat in the upcoming election.
The seat of Charlton was subsequently won for the ALP by Combet's former advisor and chief-of-staff Pat Conroy.

Since leaving Parliament Combet has worked as a consultant to unions, governments and business and as a company director.
Combet works primarily with industry superannuation funds and in December 2018 became chair of Industry Super Australia and Chair of IFM Investors, a global asset management business owned by the industry superannuation funds.

In 2020, in response to the COVID-19 Pandemic, Combet was appointed to "provide strategic and policy advice" for the Liberal Morrison Government.
On 4 May 2007 Combet announced his intention to run for the safe Labor seat of Charlton in Newcastle, New South Wales. The sitting member for Charlton, Kelly Hoare, expressed anger at losing preselection for her seat, and for a time considered running as an independent.
Combet stood down as ACTU Secretary to campaign full-time in Charlton in the lead up to the federal election. On 14 June 2007 Jeff Lawrence, National Secretary of the Liquor, Hospitality and Miscellaneous Union (LHMU) was elected unopposed as the next Secretary of the ACTU.
Combet was elected as the new member for Charlton on 24 November 2007 as part of the ALP's victory in the 2007 Australian federal election, achieving a two party preferred swing of 4.47 per cent, winning 62.87 per cent of the two party vote. Following the election, Prime Minister Kevin Rudd appointed Combet as Parliamentary Secretary for Defence Procurement in the First Rudd Ministry. He was sworn in on 3 December 2007. In February 2009, Combet was appointed Parliamentary Secretary for Climate Change, with a focus on emissions trading, to assist Climate Change Minister Senator Penny Wong.
As a result of the resignation of Defence Minister Joel Fitzgibbon and the subsequent ministerial reshuffle, Combet was promoted to the ministry on 6 June 2009, as Minister for Defence Personnel, Materiel and Science and Minister Assisting the Minister for Climate Change. Combet's portfolio was amended into April 2010 to Minister Assisting the Minister for Climate Change and Energy Efficiency and Minister for Defence Materiel and Science and to help him focus on the Government's energy efficiency programs, he axed part of this scheme—Home Insulation Program (HIP) in late April due to the safety risks and the blow-out in funding.
Combet was re-elected to Charlton at the 2010 federal election, suffering a post-redistribution two party swing of 0.24 per cent, winning 62.67 per cent of the two party vote. After Labor was returned to government in this election, Combet entered Cabinet, succeeding Wong as Minister for Climate Change and Energy Efficiency. Following the passage of the government's Clean Energy Bill, the portfolio of Industry and Innovation was added to Combet's responsibilities. Combet had decided to step down over health concerns prior to Prime Minister Gillard's defeat in a leadership spill on 26 June 2013, but brought this decision forward and announced he would step down as minister and not contest his seat in the upcoming election. The seat of Charlton was subsequently won for the ALP by Combet's former advisor and chief-of-staff Pat Conroy.
Since leaving Parliament Combet has worked as a consultant to unions, governments and business and as a company director. Combet works primarily with industry superannuation funds and in December 2018 became chair of Industry Super Australia and Chair of IFM Investors, a global asset management business owned by the industry superannuation funds.
In 2020, in response to the COVID-19 Pandemic, Combet was appointed to "provide strategic and policy advice" for the Liberal Morrison Government.
Greg Combet