Encarnacion is hitting .241 with an .888 on-base-plus-slugging percentage and 21 home runs. He will add even more power to a New York lineup that is already seventh in baseball in home runs with sluggers Aaron Judge and Giancarlo Stanton out with injuries.
ESPN was the first to report the deal.
The Yankees made it official early Sunday morning.
For the Yankees, the trade is part of a midseason push to hold off the Tampa Bay Rays and the Boston Red Sox, who started slow but have won nine of their last 14 games.
The trade allows the Mariners to dive even deeper into rebuilding mode. Seattle was set to pay the 36-year-old Encarnacion $40 million over the next two seasons, according to Spotrac.
The Yankees sent minor league pitcher Juan Then, a former Mariner, back to Seattle, along with cash considerations.