The Cathedral of St. Peter, which is also the Frascati parish church, was originally the Church of Our Lady in Vivario. As the population of Frascati grew, the church became too small for its needs, as mentioned in a report by Cardinal Bishop Alfonso Gesualdi on 16th October 1588. The new Cardinal Bishop, Tolomeo Gallo, therefore decided to build a new church and work began on 24th May 1599 with approval from Pope Clement VIII who provided 1,000 scudi for its foundation. The parish also sought financing from the funds of the Community of Frascati, from church offerings, loans from religious communities and private businesses and, from 1608 from a tax on the sale of local wine.
The façade was designed by the architect Girolamo Fontana in 1698. Five years later, Cardinal Bishop Lorenzo Corsini carried out restoration work on the apse. In 1747 clocks were placed on the two bell towers flanking the façade. In 1788 Cardinal Bishop Henry Stuart Duke of York gave the Cathedral a new organ.
In 1857 the church began to deteriorate and Cardinal Bishop Antonio Maria Cagiano de Azeredo encouraged the Frascati community to carry out restructuration work which was finished in 1858 when the Diocesan Synod was held on 24th May. Further repairs and improvements were carried out in 1908 when the flooring was treated, with special care to preserve the numerous funeral inscriptions.
On 8th September 1943, the Allied bombing of Frascati damaged the entire city and completely destroyed the Cathedral. Rebuilding, which began with the perimeter walls and façade still standing, was supervised by the Genio Civile and Bishop Biagio Budelacci and completed in 1949.
The Cathedral roof was repaired in 1965 and the façade in 2002.
The noteworthy façade was built with Tivoli travertine and stone from the quarries of Monte Porzio Catone and Frascati. It is flanked by two bell towers. There is a marble relief above the main entrance depicting Jesus handing the keys of the church to St. Peter. The interior was originally covered with frescoes, while the post war building has simple, unadorned ivory painted walls.