The $320m (€492.7m) acquisition marks the company's first ever move into the US, whose operations had previously been focused mainly on Eastern Europe.
Vivartia will acquire 100 per cent of Nonni's operations, including six production facilities, as well as the brands Nonni's, New York Style and Old London, the company said.
Chief executive officer Spriros Theodoropoulos said in a statement that once the acquisition is completed by the 1 April this year, the two companies will work together to cross-market each other's brands in both the US and Europe.
"The acquisition ensures at first the entry of Vivartia's croissant products in the US market, to be followed by other products at a later stage, while at the same time it enables Vivartia to distribute Nonni's product portfolio through its own European channels," he said.
Dennis Malamatinas, chairman of Vivartia's board of directors, said that Nonni's will also offer the company strong brand leadership in the US, one of the strongest bakery market's in the world.
"Nonni's has great brands with attractive, high-end products found from Safeway to Starbucks, and we believe it is a perfect fit for Vivartia as we expand into the North American market," he said.
Vivartia is divided into four divisions: Bakery and confectionery, frozen foods, foodservices and entertainment, and dairy and juices.
The company has operations in several countries, including Greece, Mesico, Bulgaria, Cyprus, Egypt and Russia, and claims to be the market leader in the food and beverages sector in Greece and the wider South-East region of Europe.
It also entered the Saudi Arabian bakery market last June.
In 2007, the company posted sales of $187m (€287m) and operating profit of $32m (€49.3m).