Alvarez, a 20-year-old catcher, was ranked as the No. 4 overall prospect in ESPN's midseason list published in August.
Signed as an international free agent out of Venezuela in 2018, Alvarez has had a meteoric rise through the Mets' minor league system over the past two years. He slashed .260/.374/.511 with 27 home runs this season while splitting time between Double-A Binghamton and Triple-A Syracuse.
While he missed three weeks in August with a right ankle injury, he finished the minor league season by hitting .371 with a 1.107 OPS and three home runs in his final 35 at bats for Syracuse.
A right-handed hitter, Alvarez could help the Mets at DH, especially against left-handers, against whom he hit .315 with a 1.019 OPS this season.
The Mets enter Friday night's series opener in Atlanta clinging to a one-game lead over the Braves in the NL East.
El Extrabase was first to report that Alvarez is getting called up.