ESPN's Adrian Wojnarowski first reported the deal on July 4.
The Washington Post's Tim Bontemps reported Casspi signed for the veteran's minimum, which means the Warriors still have the taxpayer mid-level exception at their disposal.
Casspi split the 2016-17 campaign between the Sacramento Kings, New Orleans Pelicans and Minnesota Timberwolves. He failed to make much of an impact during any of those stops, averaging 5.2 points and 3.1 rebounds across 36 games.
The whirlwind season represented a frustrating setback for the 29-year-old Israel native after he put together his most complete year in 2015-16. During his final full season in Sacramento, he played a career-high 27.2 minutes per game and averaged 11.8 points, 5.9 rebounds, 1.6 threes and 1.4 assists.
Casspi had the opportunity to sign with a playoff contender in March after the Pelicans released him while he recovered from a thumb injury. Instead, he joined the Wolves for the chance to work alongside a young roster down the stretch, per Jace Frederick of the Pioneer Press.
"I had a rough season with the injuries and the trade and everything that was going on," he said. "I felt like this was a place of stability and an organization that is obviously going in the right direction and everything with coach [Tom Thibodeau] and young guys I can help and they can help me. So that's why I'm looking at it."
The two-time Israeli Super League champion added: "I want to share some of my experiences and help this team win basketball games and learn how to play with them and enjoy this ride and see where it goes from there."
That's largely what Casspi brings to the table at this stage of the career. He's a solid bench asset who's capable of stepping into a bigger role on a short-term basis if needed, and he also brings experience from five NBA teams as well as time playing professionally overseas.
In the end, Casspi is on the move again as he heads for the Bay Area. While finding stability after bouncing around the league throughout his first eight years in the NBA would be ideal, the most important thing in free agency was landing on a team where he could make an impact.
He should have a chance to do so with the Warriors. Look for him to slide in as the team's primary bench sniper heading into next season.