Sources told ESPN.com Tuesday that O'Neal has agreed to a one-year deal with the Warriors, where he'll reunite with former agent Bob Myers, now Golden State's general manager.
The Warriors also agreed to a deal with free-agent point guard Toney Douglas, a source close to the situation told ESPNNewYork.com Tuesday. Terms weren't available.
O'Neal, who maintains an offseason residence in the Dallas area, also gave strong consideration to signing with the Mavericks, but ultimately grabbed Golden State's offer. The deal will be formalized this week after the league-wide moratorium on player moves is lifted Wednesday.
O'Neal, 34, had a strong bounce-back season health-wise in Phoenix in 2012-13, and credits the knee treatment he received in Germany before last season and again recently with making him feel as good as he has in years.
He averaged 8.3 points and 5.3 rebounds in 55 games for the Suns last season.
Douglas, 27, averaged 7.5 points and 2.1 assists last season in 71 games.
Douglas averaged 6.1 points and 2.6 assists in 22 games with Sacramento after the trade.
ESPNNewYork.com's Jared Zwerling contributed to this report.