Golden State trailed for most of the game but went on a 16-0 late in the third quarter and had a 92-81 lead going into the fourth quarter. Seven Warriors had at least 10 points, including Andrew Wiggins, who added 17 points, seven rebounds and five assists.
Mychal Mulder, who was playing in just his second NBA game, had 14 points and grabbed six rebounds. Former Suns player Dragan Bender had a season-high 13 points and eight rebounds.
It was the second head-scratching loss for the Suns in two days. Phoenix is still in the hunt for the eighth playoff spot in the Western Conference, but has dropped consecutive games to lowly Detroit and Golden State.
Devin Booker led the Suns with 21 points. Deandre Ayton had 20 points and nine rebounds.
Booker made a 33-foot 3-pointer just before the buzzer to give the Suns a 65-61 halftime lead.
The banged-up Warriors have fought injuries all season and were even more short-handed than usual against the Suns.
Coach Steve Kerr said before the game that Draymond Green wouldn't play because of left knee soreness, which meant the Warriors had just eight available players.
The Warriors also found out they'll be without two-time MVP guard Stephen Curry for at least a little while longer. He had hoped to play on Sunday, but instead will practice with the G-League Santa Cruz Warriors on Monday. The team said Curry is still expected to play in March.
Curry has played just four games this season after breaking his left hand in a game on Oct. 30.
Warriors: Golden State had two starters in its lineup - forward Marquese Chriss and Bender - who were drafted by the Suns in 2016. Both were disappointments in the desert. Bender was drafted fourth overall but lasted just three seasons with the organization. Chriss was drafted at No. 8 and stayed with the Suns two years. Both played well against the Suns on Saturday. Chriss had 11 points and nine rebounds.
Suns: Phoenix scored 41 points in the first quarter but then had just 40 points in the second and third quarters combined. ... Mikal Bridges scored 15 points on five 3-pointers.
Warriors: Host Washington on Sunday night.
Suns: Host Toronto on Tuesday night.
Follow David Brandt on Twitter: www.twitter.com/davidbrandtAP
More AP NBA: https://apnews.com/NBA and https://twitter.com/AP-Sports