Financial terms were not disclosed, but Beckham will reportedly earn a base salary of $1.75 million with an additional $250,000 available in incentives, according to Bob Nightengale of USA TODAY Sports.
Beckham, who will turn 29 later this month, is coming off of a 2018 season that saw him post a .661 OPS over 96 games with the Baltimore Orioles. After manning shortstop in 2017, he moved to third base to accommodate Manny Machado's switch to short.
Beckham performed better at the plate in 2017, as he went on a tear after being traded to Baltimore from the Tampa Bay Rays at the deadline, authoring a .306/.348/.523 slash line with 10 home runs over his final 50 games.
For his career, Beckham's slashed .252/.304/.424 across 384 appearances. He was drafted first overall by Tampa Bay in 2008.
The Mariners also added 23-year-old shortstop J.P. Crawford this offseason in a trade with the Philadelphia Phillies. Like Beckham, Crawford was a highly touted prospect (selected 16th overall in 2013), but owns just a .692 OPS over 72 career games to date.
In addition to Beckham, Seattle also announced the signing of right-handed reliever Cory Gearrin to a one-year contract that's reportedly worth $1.5 million with an additional $1.25 million available in incentives, according to Nightengale. The 32-year-old pitched for three teams last season, posting a 3.77 ERA with a K/9 rate of 8.3 across 62 total appearances.
To clear room on the 40-man roster for the two new signings, the Mariners designated outfielder John Andreoli for assignment.