The Mets invited Plawecki to spring training in 2015, and reassigned him to minor league camp so that he could start the 2015 season with Las Vegas. After Travis d'Arnaud went on the disabled list with a broken hand on April 19, 2015, the Mets announced they would promote Plawecki to the major leagues.
Plawecki made his Major League debut on April 21, 2015 against the Atlanta Braves. He got his first career hit off Trevor Cahill and finished the game 2-for-4, with two runs scored. During a game against the New York Yankees on April 25, 2015, Plawecki hit his first career home run off CC Sabathia en route to an 8-2 victory. Plawecki became the first player to hit his first career home run in a Mets-Yankees Subway Series game.
Plawecki and his wife, Tayler, were married in November 2015.