Nieuwenhuis was designated for assignment on May 19, 2015.
Nieuwenhuis was traded to the Los Angeles Angels of Anaheim for cash considerations on May 27, 2015. He was designated for assignment on June 10.
Nieuwenhuis was claimed by the New York Mets 17 days after the Mets traded him to the Los Angeles Angels of Anaheim. Nieuwenhuis was sent to the Las Vegas 51s and was later promoted back to the New York Mets on July 6, 2015.
On July 12, 2015, he hit three home runs in a game against the Arizona Diamondbacks. He was the first player to accomplish this at Citi Field. He is the tenth player in franchise history to hit three home runs in one game and the first to do so in a Mets' home game. When interviewed after his exceptional game that day, Kirk commented in response to his critics: "there's more to life than baseball". On July 29, Lucas Duda joined Nieuwenhuis as the second Met to accomplish the feat at home.
On September 8, 2015, Nieuwenhuis hit a pinch-hit, go-ahead home run off Jonathan Papelbon of the Nationals, breaking an eighth inning tie and handing the Mets an 8-7 win, a game in which the Mets had once trailed 7-1. After their third consecutive comeback win the next day, the Mets swept the Nats, moving themselves to 7.0 games ahead in the NL East.
On December 23, 2015, Nieuwenhuis was claimed by the Milwaukee Brewers off of waivers. Nieuwenhuis was one of nine players competing to be the Brewers center fielder for the 2016 season. On December 3, 2016, Nieuwenhuis and the Brewers agreed to a one-year, $900,000 contract for the 2017 season. He was designated for assignment on April 21, 2017.