The 26-year-old made his Major League debut with Oakland last season, batting .224 with two home runs and seven RBIs in 24 games.
Everidge started the season at Double-A Midland (Texas), was promoted to Triple-A Sacramento early in the campaign and joined the Athletics in July. He combined to bat .335 in the Minors with 20 home runs and 94 RBIs in 107 games.
Everidge was designated for assignment on Jan. 8 when the Athletics re-signed free agent Jack Cust.
The Mariners have now added three first basemen to their roster in the past two weeks, acquiring Casey Kotchman in a trade with the Red Sox for Bill Hall, a Minor League to be named and cash.
Everidge was originally selected by the A's in the 10th round of the 2004 Draft out of Sonoma State University. In six Minor League seasons, he has combined to bat .280 with 155 doubles, 108 home runs and 504 RBIs.
He led the California League with 26 home runs in '07 and led the Texas League with 115 RBIs in '08.
The Mariners' 40-man roster is now full.
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.