Etihad Airways and Alitalia will next year operate a combined 35 weekly flights between Abu Dhabi and Italy.
From March 29, Alitalia will triple its service frequency to Abu Dhabi, with new daily services from Milan and Venice. Etihad will codeshare on both routes.
Elsewhere, the codeshare expansion, which is subject to regulatory approval, will include 15 of Alitalia's domestic routes out of Rome Fiumicino airport.
Today's announcement comes less than a week after Etihad's 49 per cent stake in Alitalia was approved by the European Commission (see news, November 17).
The move will see the airlines offer combined double-daily flights to Milan and a new daily service to Venice. Etihad's EY code will be placed on both Alitalia-operated services.
Codeshares: Etihad will from March add its flight code to these Alitalia flights
The Milan to Abu Dhabi route will be operated using a B777 with 30 seats in business class, 24 in Economy Plus and 239 in economy, and will be in addition to Etihad's own daily service.
Alitalia's Venice to Abu Dhabi service will be operated using an A330-200 with 20 seats in business, 17 in Economy Plus and 213 in economy.
James Hogan, Etihad president and CEO, said: "Our codeshare agreement with Alitalia was initiated over four years ago, and the partnership has developed into a resounding commercial success.
"Importantly, we are also providing business and leisure travellers with enhanced, and soon to be unmatched, depth and breadth into and out of Italy.
"We are delighted to build on this success with the inclusion of Alitalia's daily flights from Milan to Abu Dhabi, which complements Etihad Airways' own daily service between the two cities.
"In addition, by codesharing on Alitalia's new Venice service, we will offer access to one of Italy's most popular tourist destinations for the first time, with strong demand expected not only from the GCC region, including the UAE, but also Asian markets such as China, Japan and Korea."
Last week's EC merger clearance means Etihad can now invest €560 million (£448 million) to save Alitalia from bankruptcy, as laid out in a deal signed in the summer (see news, August 8).