Gentilini has worked as director at the legal bureau of the Cassamarca until his retirement. He has been mayor of Treviso for two consecutive administrations, from 1994 to 1998 and 1998 to 2003, with the party of the Lega Nord Liga Veneta. In 2003, Paolo Gobbo was elected mayor; Gentilini became deputy mayor, as current legislation prevents mayors from serving more than two consecutive terms. Gentilini's support was decisive in the victory of Gobbo. Gentilini is a lawyer.