Garrett was lead singer of the rock band Midnight Oil from 1973 until its disbanding in 2002. He served as President of the Australian Conservation Foundation for a total of 10 years and, in 2003, was appointed a Member of the Order of Australia for his contribution to the environment and music industry.
He has been an Australian Labor Party member of the House of Representatives for the seat of Kingsford Smith, New South Wales, since October 2004. After the Labor Party won in the November 2007 election, Garrett was appointed Minister for the Environment, Heritage and the Arts by Prime Minister Kevin Rudd. On 8 March 2010, his portfolio title was changed to Environment Protection, Heritage and the Arts. He continued in this role in Julia Gillard‘s first Ministry. He was re-elected at the 2010 election and was appointed Minister for School Education, Early Childhood and Youth by Prime Minister Julia Gillard. He was sworn into this portfolio on 14 September 2010 as a member of the Second Gillard Ministry. In 2009, the French Government appointed Garrett an Officer of the Order of Arts and Letters. In 2010, WWF Australia and International presented him with their Leaders for a Living Planet award.