Iaquinta, who was part of Italy's World Cup winning squad, has penned a five-year deal with the Bianconeri.
"He is an important player, another world champion that will help us write glorious new pages in the history of Juventus," the club's managing director Jean-Claude Blanc said.
"He's a true pro, and we welcome him in our team. He has experience and other qualities to offer, and he also has the right enthusiasm and passion to satisfy our supporters."
The 27-year-old striker is delighted at making a move which would develop his footballing career.
"I have grown year after year and after seven seasons in Udine it was time to take a step forward so that I can measure myself with the challenges that only a big club like Juventus can offer me."
"It's a great challenge, I face it with enthusiasm and I'm proud to have the chance to help take this team back to the top, both in Italy and in Europe."
Iaquinta is Juventus' third acquisition after signing Bayern Munich midfielder Hasan Salihamidzic and Ajax Amsterdam defender Zdenek Grygera.
They are also linked with a move to Real Zaragoza Argentinean defender Gabriel Milito.