Montepulciano belonged originally to the diocese of Arezzo, and had a collegiate church, whose archpriest became a mitred abbot in 1400; in 1480 it became a prælatura nullius, and in 1561 was made an episcopal see.

Its first bishop was Spinello Benci (1562); among the others were: On 18 February 1984, the Vatican and the Italian State signed a new and revised concordat.

Based on the revisions, a set of Normae was issued on 15 November 1984, which was accompanied in the next year, on 3 June 1985, by enabling legislation.

According to the agreement, the practice of having one bishop govern two separate dioceses at the same time, aeque personaliter, was abolished.

There was to be only one diocesan Tribunal, in Montepulciano, and likewise one seminary, one College of Consultors, and one Priests' Council.