Assistant Don Chaney will coach the team in Saturday night's home game against the Indiana Pacers.
"We are surprised by Jeff's decision to leave the organization suddenly after 13 years," New York general manager Scott Layden said. "Jeff's coaching abilities, passion to succeed and tireless work ethic were responsible for much of the Knicks' success during his tenure. We are sorry to see him leave. We thank him and wish him well."
Layden said a decision on the coaching duties for the remainder of the season will be made as soon as possible.
Jeff Van Gundy stepped down as coach of the New York Knicks on Saturday.(AP/Jeff Zelevansky)
No reason was given for Van Gundy's departure, but he ended practice 15 minutes early on Friday, upset with the team's level of intensity.
The Knicks started slowly this season with just four victories in their first 11 games, but have won five of their past six contests and are in fourth place in the Atlantic Division with a 10-9 record.
Van Gundy, 39, was in his seventh season as Knicks' coach.
During the lockout-shortened 1999 season, Van Gundy guided the Knicks to the NBA Finals, where they lost to the San Antonio Spurs.
