Pereyra, 23, arrived at the club for a medical on Wednesday and the Italian champions - who have the option to make the deal permanent at the end of the season - have now confirmed the transfer.
Juventus will pay an initial €1.5 million, while a fee of €14 million will be paid over three years if the deal is made permanent, with further add-ons included if Pereyra achieves certain targets.
"Juventus football club can today announce that Roberto Maximiliano Pereyra has completed a move to the club after terms were agreed with Udinese on a one-season loan deal for a fee of €1.5 million," read a statement on the club's official website.
"The agreement includes the option for Juventus to make the deal permanent at the end of the 2014-15 campaign for a price of €14 million, to be paid over the course of three years.
"This fee could be increased by €1.5 million should Pereyra achieve certain pre-defined sporting targets by 30 June 2020."
Pereyra has made 84 Serie A appearances during his three-year spell at Udinese, scoring eight goals.
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