Familia, 29, served as the Mets closer for parts of four seasons before being traded to the Oakland Athletics last July. He posted a 3.13 ERA, 1.22 WHIP, and 83 strikeouts in 72 innings split between the two clubs last year.
While Familia owns the Mets' single-season franchise saves record (51), he's not expected to close for New York this time around. General manager Brodie Van Wagenen traded for All-Star closer Edwin Diaz earlier this month, so Familia will likely serve as the setup man.
Familia, the first high-profile reliever to sign this winter, pitched in a similar role for Oakland ahead of All-Star closer Blake Treinen, posting a 3.45 ERA, 1.21 WHIP, and 40 strikeouts over 31 1/3 innings.
Van Wagenen prioritized upgrading the bullpen after taking over in October, and will likely now shift his focus to acquiring a starting catcher.