Roch Kubatko of MASN first reported that the two sides had agreed to terms on a deal.
Alvarez will be playing his third season with the Orioles organization after the club signed him to minor-league deals in each of the last two years. Last year, the 31-year-old slugger played mostly in the minors before being called up to Baltimore in September, when he slashed .313/.353/.438 with one home run and four RBI in 14 games. In 2016, Alvarez played in 109 games with Baltimore, smacking 22 home runs with 49 RBI while slashing .249/.322/.504 as mostly its designated hitter
Before his recent stint with the O’s, Alvarez had spent six seasons with the Pirates, who drafted him second overall in 2008. Playing primarily as their third baseman, Alvarez hit 131 homers with 454 RBI while slashing .236/.309/.441. His best season was in 2013, when he blasted a National League-high 36 homers and knocked in 100 runs en route to an All-Star appearance and a Silver Slugger award.
Alvarez will be an insurance policy for the Orioles in case Mark Trumbo, Chris Davis or Trey Mancini gets hurt.