Smith's tough jumper from 15 feet had tied it at 97 with 10.6 seconds left. Then, after the turnover, Jason Kidd inbounded to Smith, who got the shot off as he sailed toward the out of bounds line. Smith scored 27 and Kidd 23.
Jared Dudley had a career-high 36 for Phoenix, including two free throws that put the Suns ahead 97-95 with 34.5 seconds to go.
New York was without the NBA's No. 2 scorer Carmelo Anthony (hyperextended knee) and Raymond Felton (sprained finger), both hurt in the Christmas day loss to the Lakers in Los
The Knicks said X-rays on Felton's right fifth finger revealed a fracture and the next course of action will be determined after his return to New York.
The Suns lost Goran Dragic in the final seconds of the first half when he was undercut by Smith on a layup attempt and fell hard to the floor. Dragic had bruises to his hip, back and wrist. Smith was called for a flagrant foul on the play.
Chris Copeland and Tyson Chandler added 14 points apiece for the Knicks.
Dudley, whose previous high was 33, was 11 of 17 shooting, 5 of 8 on 3s, and 9 of 9 at the foul line. Marcin Gortat added 13 points for the Suns, who lost their third in a row.
New York led 54-44 at the half and stretched it to 68-54 when
It was knotted at 76 entering the fourth.
Dudley was fouled by Copeland on a 3-point try and made all three free throws to put Phoenix up
After a scoreless 1:28, Sebastian Telfair made a 3, then Brown sank a 20-footer to tie it at 95 with 1:15 remaining.
Smith missed a jumper from the top of the key 52 seconds from the finish and the Suns got the ball. Dudley was fouled on a drive to the hoop and made both free throws to make it 97-95.
But Smith, with P.J. Tucker all over him, sank a fade-away from just outside the free throw line with 10.6 seconds remaining to tie.
Phoenix coach Alvin Gentry called a 20-second timeout but the play broke down and, when Telfair tried to hit Marcin Gortat for a
After a timeout, Kidd tossed the inbounds pass to Smith, who got the shot off, again over Tucker, from just inside the 3-point line. It went in and he was mobbed by his teammates.
The Knicks were missing a little over 43 points per game without Anthony and Felton, the first game this season that New York had been without both of its top two scorers. Rasheed Wallace also was out with a sore left foot.
Notes: The Knicks complete their brief three-game trip west at Sacramento on Friday. ... New York has lost two in a row only once this season. ... Michael Beasley, a big part of the second-half surge, missed Sunday's home loss to the Clippers due to illness.