Ihattaren has signed a four-year deal with Juve having arrived for a fee reported to be in the region of €5-6million.
The 19-year-old playmaker, who had less than a year remaining on his PSV contract, must wait for his Bianconeri debut after he was allowed to join Serie A rivals Sampdoria for the remainder of the season.
Ihattaren made his PSV debut aged 16 and went on to score 10 goals in 74 appearances for the Eredivisie side.
PSV director of football John de Jong said: "Mohamed has gone through ups and downs in the last few years. As a young prospect, his career got off to a bright start but it has taken a turn and he has not fulfilled his potential for various reasons.
"It is a great pity, in particular for Mohamed himself. We are happy for Mohamed that he has made a move to Italy and hope he will live up to his potential."
Radu Dragusin has also made the move from Juve to Sampdoria for the rest of the campaign.
Juventus earlier brought Moise Kean back to the club from Everton on a two-year loan with an obligation to buy following the departure of Cristiano Ronaldo to Manchester United.
Kean returns to Turin two years after the forward left for the Premier League in a £27million (€31.5m) move, having signed a five-year deal with the Toffees.
Juve will pay €7m (£6m) for the striker's loan spell, payable over two years. They will be obliged to re-sign him on a permanent basis for a fee that could reach €31m (£26.6m) if certain objectives are met.