The most important archeological finding, dating back to Ancient Roman time, during the late Republican Age, is a patrician Roman villa probably belonging to Lucullus. In the first century AD the owner was Caius Passienus Crispus, who married Agrippina the Younger, mother of Nero. Later his properties were confiscated by the Flavian imperial dynasty (69 - 96 AD). Consul Flavius Clemens lived in the villa with his wife Domitilla during the rule of Domitian.

According to the Liber Pontificalis, in the 9th century Frascati was a little village, probably founded two centuries earlier. The name of the city probably comes from a typical local tradition of collecting firewood ("frasche" in Italian): many place-names around the town refer to trees or wood. After the destruction of Tusculum in 1191, the town population increased and the bishopric moved out from Tusculum to Frascati. Pope Innocent III endorsed the city as a feudal possession of the basilica of San Giovanni in Laterano, but in the following centuries its territories was ravaged by frequent raids that impoverished it. It was a possession of various baronal families, including the Colonna, until, in 1460, Pope Pius II fortified the place with walls.

At the beginning of the sixteenth century Pope Julius II gave Frascati as a feudal possession to the condottiero Marcantonio I Colonna, who lived there from 1508 together with his wife Lucrezia della Rovere, nephew of Pope Julius II. In 1515 Marcantonio Colonna gave to Frascati the "Statuti e Capituli del Castello di Frascati", it was the first city statute with the rules and regulations to observe.

In 1518 a Hospital was built, named after St. Sebastiano, in memory of the old basilica destroyed in the 9th century. After Prince Colonna's death in 1522 Lucrezia della Rovere sold Frascati to Pier Luigi Farnese, nephew of Pope Paul III.

On May 1, 1527 a Landsknecht company, after having sacked Rome, arrived out of the bordering villages. However, the soldiers changed direction of march next to a niche consecrated to the Virgin Mary, and the town was therefore safe. This event is commemorated by a church now called Capocroce.

In 1538, the Pope Paul III conferred the title of "Civitas" to Frascati, with the name "TUSCULUM NOVUM". In 1598 construction began of a new cathedral dedicated to St. Peter.

On September 15, 1616 the first no-aristocratic, public and free school in Europe, started up by the initiative of Saint Joseph Calasanz.

On June 18, 1656 a part of plaster peeled off the wall inside the Church of St. Mary in Vivario and an ancient fresco became visible, it was the image of Saints Sebastian and Roch protector from the plague. In that year there was an epidemic of plague in Rome (anno dirae luis) but Frascati was safe, from that year the two Saints were co-patron Saints of the city. The statues of these Saints are in the facade of the Cathedral.
In 1757 the Valle theater opened in the centre of the town. And in 1761 the fortress changed to a princely palace under the patronage of the Cardinal Henry Stuart duke of York.

In 1809 Frascati was annexed to the French Empire, and selected as capital of the Roman canton.

In autumn 1837, there was a plague epidemic in Rome, and 5,000 people left Rome. Frascati was the only city that opened its doors to them. Since then Frascati's flag has been the same as Rome's, yellow and red.

In 1856 the city was chosen as the terminus of the first railway (Rome and Frascati Rail Road) to be built by the Papal State. The last section of the railway line was inaugurated in 1884, 14 years after the city became part of the new Kingdom of Italy. On December 17, 1901 the first electricity reached Frascati from a hydroelectric plant in Tivoli.

In 1906 the electric tram line was opened for service between Frascati, Rome and Castelli Romani, they traveled wholly along tracks laid down in streets as interurban electric streetcar (light rail). In 1954 the electric Tram line was replaced by buses.

In 1943, during World War II, Frascati was heavily bombed (Frascati bombing raid September 8, 1943). About 50% of buildings, many of the monuments, villas and houses were destroyed, and many people died. A second bombing raid on January 22, 1944, the day of the battle of Anzio (Operation Shingle). The city was liberated from the German occupation on June 4, 1944 by U.S. 85th Infantry Division.

In 1944-1945 the ruins of the buildings were carried to filled in a valley, now in that place there is the "8 September Stadium".

In 1954 the mayor Micara made an exchange of real property with Duke Andrea Torlonia, between the "Quadrato estate" near Rome and the "Gardens of Villa Torlonia", so them became public park.

Frascati is famous for its notable villas of the Papal Nobility, built from the 16th century by the Popes, cardinals and Roman nobles as "status symbols" of Roman aristocracy, they were destined to social activities rather than farming. The "Ville Pontificie" have very particular relationship with the surrounding landscape. The villas are substantially well preserved, damages caused to some of them during World War II have been repaired following the original techniques and materials with correct methodologies.

These are:

Villa Aldobrandini

Villa Parisi

Villa Falconieri

Villa Grazioli

Villa Lancellotti

Villa Muti

Villa Rufinella (or Tuscolana)

Villa Sora

Villa Torlonia

Villa Vecchia

Villa Mondragone

Villa Sciarra