The Giants secured the 30-year-old's services one day after they officially traded Beckham to the Cleveland Browns.
Giants general manager Dave Gettleman assured fans after trading Beckham, a prolific pass-catcher in the prime of his career, that the club was still determined to field a winning team in 2019.
"You can win while you build a roster," he said. "We do have a plan, and this is a part of it."
Tate comes to New York as one of the best possession receivers in the NFL. He was widely viewed as the top player at his position available in free agency.
The Notre Dame product posted 795 yards and four touchdowns last season, though he was on pace to eclipse 1,000 yards before the Detroit Lions shipped him to the Philadelphia Eagles at the trade deadline.
Tate has split his nine-year career between the Eagles, Lions, and Seattle Seahawks.