The move follows Cassina's appointment last year of Spanish designer Patricia Urquiola as its creative director, and Driade's hiring of British architect David Chipperfield in 2014.
Giulia Molteni, the brand's head of marketing and communication, said the appointment would help the family-run company distinguish itself from other Italian brands.
"I think Vincent will give us a more sophisticated look, a bit of northern European minimalism that Molteni needs," she told Dezeen.
Molteni admitted that Italian furniture brands have been difficult to tell apart, since they tend to work with the same roster of international designers.
"It's true, it's definitely true [the Italian brands can be hard to tell apart]," she said. "There's a kind of Italian mood that's spread all around."
She added: "I think Vincent will work very much on interior decoration to give a real sense of home, because of his experience in architecture, and to keep the image very high and sophisticated and different from everybody else."
As well as introducing new products, Urquiola has refreshed the brand's back catalogue of classics such as Gerrit Rietvelt's Utrecht chair, which was relaunched with a limited-edition fabric by Bertjan Pot.
"I love it, it's amazing," said Molteni of Urquiola's rethinking of Cassina. "Really, really high-end design again for Cassina."
"We're very happy for her but I will miss her!" she added, referring to the fact that with her contract with Cassina, Urquiola is no longer quite so free as before to work with other brands.
Urquiola's work at Cassina is reminiscent of Hella Jongerius' impact at Vitra where, as creative director of colours, textiles and surfaces, she has refreshed the brand's archive with new fabrics and colours.
Van Duysen is Molteni's first creative director since the 1990s, when Italian designer Luca Meda held the role. Since then Carlo Molteni, the brand's president and Giulia's father, has provided creative direction.
Van Duysen said: "I am proud that Carlo Molteni has now entrusted me with the creative coordination of Molteni&C and Dada, brands with an extraordinary history and with DNA linked to the great names of architecture, such as Aldo Rossi, Tobia Scarpa and Luca Meda".
The designer will focus on refreshing the brand's image as well as working on its exhibition stands and retail stores. He designed both the Molteni&C and Dada stands at the Salone del Mobile this year, and will design Molteni&C's new Tokyo flagship store, which is due to open this autumn.