Crawford was averaging 19.6 points and 4.4 assists through 11 games this season for the Knicks. In his ninth NBA season, Crawford owns averages of 14.7 points and 4.1 assists.
Harrington, meanwhile, has averaged 12.4 points and 5.6 rebounds in five games for the Warriors this season. He has career averages of 13 points and 5.8 rebounds in 660 games over 11 NBA seasons with Indiana, Atlanta and Golden State.
Harrington was the 25th overall selection in the 1998 NBA Draft by the Pacers, when current Knicks president Donnie Walsh was in Indiana's front office.
"I drafted Al back in 1998 and I think his talents are a great fit for our style of play," Walsh said. "This trade also gives us more long-term flexibility while enabling us to remain competitive this season."
Crawford's contract runs through 2011, while Harrington's expires after the 2009-10 season.