Channing Frye had 19 points and 11 rebounds, and Grant Hill scored 18 to help the Suns build a 23-point lead and hold on late. They made 13 3-pointers and shot 43 percent from the floor.
Monta Ellis scored 21 points and David Lee had 16 points and 10 rebounds for the Warriors, who got within five in the fourth quarter but could not come all the way back.
This was the vintage Suns on display for most of the night.
They shot themselves to victory with an array of outside jumpers that even the usually high-scoring Warriors couldn't match. Phoenix went 9 for 15 on 3-pointers in first half, with five different players sinking shots from beyond the arc.
Nash had eight first-half assists, and Frye and Mickael Pietrus - who turned 29 on Monday - each made three 3-pointers to put Phoenix up by 20 in the second.
Suns coach Alvin Gentry perhaps removed his starters a little too quickly in a game that appeared over.
The Warriors got within 93-88 with about 4 minutes remaining in the fourth quarter in a frantic rally that fell short. They scored 11 straight points during the spurt, helped by Phoenix missing eight straight shots with most of its starters on the bench, but just couldn't sustain the momentum.
Nash and Co. shed their warmups and quickly put the game away. Frye made a 3-pointer and another jumper, Nash hit a pull-up shot and the Suns went back ahead 104-90 in about a minute.
The Suns have won four of their last five and are in the thick of the playoff race. They began the day 2½ games behind Portland for the final Western Conference playoff spot, with Memphis sandwiched between them by percentage points.
Phoenix did enough damage early to put any kind of comeback far out of reach.
The frenetic pace and slick ball movement by Nash and the Suns were too much for the defensively challenged Warriors to keep up. Phoenix went ahead 77-54, shot 61 percent through three quarters and built enough of a cushion to withstand the Warriors' push.
NOTES: The Suns sang happy birthday to Nash and Pietrus before the game in the locker room in an acapella rendition. "It came out really nice," coach Alvin Gentry said, chuckling. ... Phoenix G Goran Dragic missed his fourth straight game after cutting his left foot stepping on a piece of broken glass at his home, requiring nine stitches. ... Nash had not played on his birthday since 2004, when he had 29 points and 11 assists against Dallas. ... Warriors backup G Acie Law missed his second game in a row with a sprained right wrist. ... The Suns and Warriors play again Thursday in Phoenix.