Born in Whanganui, Don moved with his family to Christchurch at the age of six. After studying economics, history and political science at the University of Canterbury, he completed a master's, then PhD in economics. He later secured a job as an economist at the World Bank in the United States.
Upon returning to New Zealand in 1971 he worked in various banking roles and first dipped his toe into politics in 1980, standing unsuccessfully as the National Party candidate in the East Coast Bays electorate.
In 1988 Don began a 14 year tenure as Governor of the Reserve Bank. In 2002 Don resigned his post to stand again for parliament, placing 5th on the National Party list. After a year in parliament as National's finance spokesperson, Don Brash challenged and unseated Bill English as the leader the party and became the Leader of the Opposition.
Don resigned from parliament in 2006, and has continued to be a significant voice in the New Zealand political landscape.