Wendy Duncan was born in Kalgoorlie, Western Australia, to Shirley Maxine (née Davies) and Stephen John Tonkin. She and her siblings were raised on her parents’ sheep station, and received their early education from the School of the Air. Duncan later boarded at Methodist Ladies’ College, Perth. After leaving school, she spent a year in South Africa through the Rotary Youth Exchange, and then enrolled at the University of Western Australia, eventually graduating with a Bachelor of Arts degree in politics and Australian history. Duncan worked for the National Farmers’ Federation in Canberra from 1977 to 1979, and also completed a postgraduate diploma at the Canberra College of Advanced Education (now the University of Canberra).
From 1994 to 1998, Duncan worked as a research officer for Ross Ainsworth, a long-serving Nationals MLA for the seat of Roe. She joined the party herself in 2001, and from 2002 to 2003 served as president of the party’s Esperance branch. Duncan served on the party’s state executive from 2003 to 2004, and then from 2004 to 2008 served as state president, becoming the first woman to hold the position. During her presidency, she was one of the architects of the party’s Royalties for Regions policy. In January 2008 Wendy Duncan took up a position on the Legislative Council. In her inaugural speech, she expressed concerns about foreign ownership of Australian resources, economic rationalism, the dominance of the two major parties and the neglect of regional and rural areas.
At the 2008 state election, Duncan transferred to the Mining and Pastoral Region. She was subsequently included in the new ministry formed by Colin Barnett of the Liberal Party, becoming parliamentary secretary to the Minister for Regional Development and Minister for Lands, and also assistant minister to the Minister for State Development and the Minister for Transport. In April 2012, Duncan won preselection for the seat of Kalgoorlie at the 2013 state election. At the election, in April 2013, she received 56.3 percent of the two-candidate-preferred vote, becoming the first member of the party to win the seat since its creation in 1901. Wendy joined the WASM Alumni Patrons in 2016