According to tradition, Canosa, then called Canusium, was founded by the Homeric hero Diomedes. Historically, it was one of the main center of the Dauni, in an area where human presence dates back from the 7th millennium BC.

The Bridge on Ofanto river near Canosa di Puglia.

In 318 BC the city allied with Rome, helping the Romans after their defeat at Cannae (216 BC). It became a Roman municipium in 88 BC and was a flourishing center for the production of wool. In 109 AD it was reached by the Via Traiana and in 141 an aqueduct brought fresh water ot the city. In the late 3rd century it became the capital of the Provincia Apuliae et Calabriae. In the following century it was the most important Christian diocese of southern Italy, famous as the "Bishop's City" and reaching the peak of its splendour under bishop Stercorius (343), bishop St. Sabinus (514-566).

Under the Lombards, it was the seat of the Gastaldate, and in the following centuries suffered several Saracen attacks. Under the Normans (11th-12th centuries) Canosa recovered some importance, in particular thanks to prince Bohemund of Hauteville. However, after the end of the Hohenstaufen domination in Italy, it went into a decline that lasted until the 18th century: in this period it was ruled by the Orsini del Balzo, Grimaldi of Monaco, Affaitati and Capece Minutolo families.