The two football federations had been competing in the bidding contest that is scheduled for an Oct. 10 vote by UEFA executive committee members.
Teaming up would reduce UEFA's risk of committing to a solo host for a 24-team, 51-game tournament nine years in advance.
Italy need to build and renovate an aging inventory of stadiums. Construction projects in Italy, such as replacing iconic San Siro stadium in Milan, can be notoriously bureaucratic and slow.
Turkey have the stadiums and infrastructure almost entirely ready after a massive national construction project under two decades of President Recep Tayyip Erdoğan's political leadership.
Co-hosting without a competitive vote would be a pragmatic solution for Turkey after several failed bids over the last 20 years and fresh questions over their hosting ability after Manchester City fans faced logistical challenges at the UEFA Champions League final in Istanbul last month.
UEFA said it will now work with the two federations to ensure their joint bid meets all the requirements for the 24-team tournament.
Turkey are also bidding to host the 2028 edition, though that has long been expected to go to the joint bid by the four United Kingdom federations and Ireland.
The UK and Ireland focused on a Euro 2028 bid with UEFA's approval when they ended a plan to be Europe's preferred candidate to host the 2030 World Cup against competition from the Spain-Portugal bid. That project now also includes Morocco and Ukraine. The FIFA vote is scheduled late in 2024.
UEFA should make both Euros hosting awards on Oct. 10 in Nyon.
Euro 2024 is being hosted alone by Germany, who easily beat Turkey in a vote in September 2018.