The trade has the Knicks sending Porzingis and guards Courtney Lee and Tim Hardaway Jr. to Dallas in exchange for DeAndre Jordan, Wesley Matthews and Dennis Smith Jr. The deal also might include draft assets, with the Mavericks hoping to acquire a first-round selection.
Sources told ESPN the clubs scheduled a trade call with the league office to finalize the agreement.
The contracts of Jordan and Matthews expire at season's end. Porzingis can become a restricted free agent this summer, and it remains unclear whether he'll choose to re-sign with the Mavs.
Sources told ESPN that Porzingis met with Knicks management earlier Thursday and gave the impression he wanted to be traded. He expressed his frustration about the current state of the team and his future with the organization.
Porzingis has been sidelined for nearly a year as he recovers from an ACL injury sustained last season. He was averaging a career-high 22.7 points per game before going down in his breakout All-Star campaign.
The Knicks have struggled without Porzingis this year, posting a 10-40 record.