First elected in November 2002, he had previously served one term in the Minnesota House of Representatives, representing District 60B. He was re-elected to the senate in 2006 for a term ending 2010.
He attended both the University of Minnesota and the University of St. Thomas in Saint Paul.
Dibble is openly gay; his partner is Richard Leyva. He is one of three gay members of the Minnesota Legislature, alongside Sen. Paul Koering (R–Fort Ripley) and Rep. Karen Clark (D–Minneapolis). His campaigns have won the support of the Gay & Lesbian Victory Fund.