Demiral impressed in a half-season with Sassuolo in 2018-19, making 14 Serie A starts after his loan move from Turkish side Alanyaspor.
Sassuolo will make that loan permanent on July 1, and are now set to sell the Turkish international to the Serie A champions.
Demiral will join the Bianconeri on a five-year contract.
Juventus fought off late interest from Atletico Madrid in Demiral, who can play at centre-back and at right-back.
Juve are set to evaluate Demiral in the pre-season before determining whether to keep him on the team or send him out on loan for more seasoning.
But the club are high on the Turkish defender, who will join Giorgio Chiellini, Leonardo Bonucci, and Daniele Rugani in the heart of the Juve back line.
The club are likely to add another defender as the summer window goes on, but first must contend with the business of finding a new manager.
Juventus announced the departure of Massimiliano Allegri last month, after the manager won the Serie A title in all five of his seasons in charge.
Chelsea's Maurizio Sarri is the leading candidate to take over, as Goal reported last week that the 60-year-old has reached an agreement with Juventus to become the Serie A champions' next head coach.
After Sarri makes his return to Juventus, the club are likely to add more talent in the summer as they chase their first Champions League title since 1995-96.
Juventus are open to selling striker Mario Mandzukic and Goal understands they will listen to offers this summer for the Croatia international, with Sarri again set to lean on his strong relationship with Gonzalo Higuain to bring the Argentine in as a replacement.
Fiorentina's Federico Chiesa is another of the club's reported midfield targets.