The Italy goalkeeper joins on loan until 30 June 2027, with Juventus holding the right to make the deal permanent for a fee of €8million plus a further €2million in bonuses.
Speaking to the club's official channels, Vicario did not hide his emotion at completing the move.
"Honestly, the emotion is huge, because it's a bit of a dream come true," he said. "Ever since I was a child I've dreamed of and hoped for this moment.
"Obviously you never have any certainty that you'll manage to do it, so I'm extremely proud of myself, for my family, for having made it happen."
He went on to explain what representing Juventus means to him, framing the move as the pinnacle of his career ambitions.
"Because for me, having the opportunity to represent Juventus means the absolute maximum you can ask of life in terms of ambition," he said. "So that's the thing I want to stress most, because representing these colours, this club, this history is a huge sense of responsibility that I'm absolutely happy to take on, and I feel it right from my heart. It's something I'm still struggling to fully process, but I'm extremely happy."
Vicario, 29, spent three seasons in England after Tottenham signed him from Empoli in 2023 for an undisclosed fee, going on to make 117 appearances and win the Europa League in 2025. His arrival in Turin gives Juventus a new first-choice option in goal following a lengthy search that had previously included interest in Liverpool's Alisson Becker, Aston Villa's Emiliano Martinez and Parma's Zion Suzuki.
Tottenham had initially preferred a deal including an obligation to buy, but ultimately agreed to the loan structure given Vicario's strong desire to leave London and return to Italian football.
He arrived in Turin to complete his medical before signing his contract, with head coach Luciano Spalletti expected to hand him an immediate debut once the domestic season gets under way.