Born and raised in Texas, Don Haslam earned a degree in economics at the University of Chicago, where he was quarterback and pitcher on NCAA teams. After graduation, he traded financial futures on the floors of the Chicago Board of Trade and the Chicago Mercantile Exchange. He joined several large banks as a bond and currency trader, including NationsBank Texas, where he managed a bond portfolio in excess of $50 million. He put himself through the University of Tulsa Law School while Vice President and foreign exchange trader at Liberty Bank & Trust in Tulsa.

Haslam joined Riggs, Abney, Neal, Turpen, Orbison and Lewis, one of Oklahoma's largest law firms, where his work focused on business transactions for large clients such as EMSA, the Tulsa County Criminal Justice Authority, Case Properties, and others.

He serves as Chancellor for the Diocese of the Southwestern States [the Anglican Church]. He is a board member of Domestic Abuse Helpline for Men and Women, a national organization that assists people in abusive relationships and rejects the myth that these relationships most often afflict women.