Emmi, which declined to disclose a fee for the deal, said it saw Italy as a key fresh dairy market, and would look to use Trentinalatte to improve its presence in fast-growing yoghurt and yoghurt drinks sectors.
Trentinalatte had sales of €35m in 2005.
The deal caps another week of consolidation in Europe's dairy industry, following Arla Foods' agreement to buy fellow Danish cheesemaker Tholstrup.
Emmi said its takeover of Trentinalatte would give it access to a newly built, state-of-the-art production facility, which would help it to increase capacity and develop more new products.
Walter Huber, Emmi's chief executive, said the deal would help Emmi hold off rising competition in the fresh dairy sector.
The Swiss group posted record sales of nearly €1.3bn for 2005, helped on by the launch of Choco Latte and yoghurt drink Evolus in Portugal and Switzerland, as well as the launch of its first ice cream range.
A string of acquisitions across the European dairy sector have made competition more intense, however.
French group Lactalis has been particularly active, creating one of Europe's largest fresh dairy firms late last year via a joint-venture with Nestlé, and then moving on to buy out Italian speciality cheesemaker Galbani.
The Nestlé-Lactalis venture will compete against established companies such as Danone, Arla Foods and Campina; all of which have sought to improve their presence in higher value, fresh dairy products.
The European Commission predicted earlier this year that consumption products like these, including yoghurt and cheese, would rise across Europe up to 2012.