He was born in Garland, Arkansas and grew up in Exeter, California, then went to Fresno State University where he received degrees in physical education in 1959 and 1965, followed by a doctorate in education from Utah State University in 1970.
In 1964, he started work for the Clark County School District of Clark County, Nevada (the county of Las Vegas), eventually becoming superintendent of schools. In 1978, he shifted to business and joined PriMerit Bank, becoming chairman of the board in 1987, then moving to Southwest Gas Corporation, where he was chairman by 1993.
In 1994 he was interim president of University of Nevada, Las Vegas.
As governor, Guinn has developed a reputation as a moderate Republican with an appeal to many Democrats; in the 2002 election, he garnered 68% of the vote versus Democrat Joe Neal's 22%, which meant that a significant number of Democrats voted for Guinn.