Nieuwenhuis had been designated for assignment by the Mets on May 19. He was 3-for-38 this season.
The Mets will receive cash from the Angels.
Nieuwenhuis was out of options, so the Mets would have needed to pass him through waivers in order to send him to Triple-A Las Vegas.
Overall, Nieuwenhuis has a .230 average with 13 homers and 60 RBIs in 527 career at-bats.