The Mali international has signed a five-year contract with the Italian club.
The midfielder struggled to hold down a regular first-team place at Liverpool this season after falling out of favour under manager Rafael Benitez.
Sissoko has welcomed the move to Juve and believes the switch will allow him to progress in his career.
"I'm happy to have joined such an important club, this move certainly constitutes a step forward in my career," he told the Juventus TV channel.
"I feel very excited to think about the possibility of playing with great players such as (Gianluigi) Buffon and (Alessandro) Del Piero and to work under Ranieri, a great coach who I already know from my time at Valencia."
And Juventus director Jean-Claude Blanc believes Sissoko will bring experience to the club.
"He is an important element in the strengthening of our squad," added Blanc.
"Despite being only 23, Sissoko is a player of great experience having played more than 30 UEFA Champions League matches. He has also played many matches in big leagues and for his country."