The 38-year-old will be with the Cavs for the remainder of the season, NBA insider Shams Charania reported.
Varejao was the 30th overall pick in the 2004 NBA Draft. He was with the Cavaliers for 12 years, including both Cleveland stints from LeBron James.
He signed with the Warriors in 2016 and faced his former team in the NBA Finals, which resulted in the Cavs championship.
Most recently, Varejao played with the Brazilian team Flamengo.