Treen was born in Baton Rouge to Joseph Paul Treen, Sr. (1900–1986) and the former Elizabeth Speir (1899–1990). He had a second brother, Paul Treen, Jr. He is married to the former Martha Ann Swayze (born 1928).
Treen has long been active in the Louisiana Republican Party. While Dave Treen ran for governor on February 1, 1972, in the first of three campaigns for the state's highest office, John Treen in that same election contested a Louisiana State Senate seat in Jefferson Parish. He lost by 973 votes to the Democrat, M. Joseph Tiemann.
In late 1988, Republican State Representative Charles Cusimano resigned from the Louisiana House (District 81) after eight years to accept a position as a 24th Judicial District Court judge. In the special election, the candidates included Treen, Duke, Republican school board member Delton Charles, Democratic real estate agent D.J. "Bud" Olister (backed by Jefferson Parish Sheriff Harry Lee), and Roger F. Villere, Jr., a young businessman from Metairie who was named the Republican state chairman in 2004. Duke finished first in the primary with 3,995 votes (33.1 percent). Because no candidate received a majority in the first round, a runoff was required between Duke and Treen, who polled 2,277 votes (18.9 percent) in the first round of balloting.
David Vitter, then a young Republican attorney, would have entered the special election had he met the residency requirement. Vitter would become the representative for District 81 in 1992 and then win election to the United States House of Representatives.."