The 37-year-old has been brought back to Turin to provide cover for Guglielmo Vicario, with Grabara facing a lengthy spell on the sidelines following a cruciate ligament injury.
Juventus confirmed the move on Monday, bringing Neto back to the club eight years after he initially left.
"Norberto Neto returns to wear the Juventus shirt. The Brazilian goalkeeper joins the Bianconeri again until June 30, 2027," the club announced.
Neto previously spent two seasons with Juventus between 2015 and 2017, making 22 appearances and winning two Serie A titles, two Coppa Italia trophies and the Italian Super Cup.
His career subsequently took him to Spain, where he played for Valencia and Barcelona, before three seasons in England with Bournemouth and Arsenal. He returned to Brazil last season with Botafogo.
Neto admitted that returning to Juventus feels very different from his first spell because of everything that has happened during the intervening years.
"Coming back here is a déjà-vu. I would like to thank the club, the director and the coach for this opportunity and this possibility. I'm really happy," he told Juventus' official channels.
"It seems difficult to believe that I can come back here with a blank page to write, knowing already what I've experienced, what the club is like and what the environment is like. So I'm really happy."
The goalkeeper said his first spell in Turin had been an important stage of his career before a journey that took him through several countries.
"For me, being here the first time was really an important step in my career. Then I had the opportunity to travel a lot, covering many kilometres and getting to know other cultures and places," Neto said.
He also revealed that he had spoken to Juventus coach Luciano Spalletti before accepting the move.
"I heard from the coach on the phone. I was in Brazil, he called me and asked how I was and whether I wanted to take on this experience and adventure," Neto said.
"I don't think there was any need to answer. It made me really happy to hear from him and I'm very happy."
Neto also sent his best wishes to Grabara as the injured goalkeeper begins his recovery.
"I'd like to wish him all the best and give him a lot of strength for his recovery," he said. "Unfortunately, these are things that happen in our position and we are really sorry."
Neto will wear the number 33 shirt and said he sees his role as extending beyond simply providing cover.
"I expect a season of great growth and to achieve great objectives with these young players who are trying to build their own history at an important club like Juventus," he said.
"I'd really like to be important on a human level, to help when necessary and be available for whatever opportunity and for everything that can be important for the club."