Once awarded, the $1.23bn (€1.032bn) contract will involve Webuild managing works for Rete Ferroviaria Italiana (Gruppo FS Italiane).
The works will be executed by a consortium, in which Webuild has a 70% stake while Pizzarotti owns the remaining 30%.
Earlier, an additional 11.8km section of the same line between Orsara and Bovino was awarded at a value of $437.09m (€367.2m).
This contract is part of the modernisation of the railway between Bari and Naples.
The Orsara-Hirpinia section is being planned to be included in the fifth corridor of the Trans-European Transport Network (TEN-T), which would operate between Helsinki and Valetta.
This new section will extend for 28km, with nearly 27km running in a tunnel.
The trains operating on this line are expected to run at a speed of 250km/h.
Meanwhile, the Bovino-Orsara section will commence operations briefly with the construction of a temporary link to the historic line beside the current Orsara station.
With the demolition of the temporary rail link, the project will commence on the Bari side, next to the railway already constructed for the Bovino-Orsara section.
The 314m Cervaro Viaduct begins after a briefly raised portion, which connects to the 27km Hirpinia tunnel on the Naples side.
In a statement, Webuild said: “The Naples-Bari high-speed railway will be a strategic axis in the development of sustainable mobility in southern Italy. It will reduce by about half the time it takes to travel between Naples and Bari to just two hours.
“It will also bring northern and southern Italy closer together, bringing the travel time between Milan and Bari down to six hours.”
Last week, Webuild and its US unit Lane Construction signed the final agreement with Texas Central for a $16bn contract to build a high-speed railway between Dallas and Houston.