In addition to Choi, the O's signed pitchers Pedro Beato, Todd Redmond, Cesar Cabral and Ashur Tolliver, infielders Ozzie Martinez and Steve Tolleson and catcher Audry Perez.
Tolleson, 32, has hit .294/.348/.469 in 115 Major League games against left-handed pitchers.
The 6-foot-1, 230-pound Choi posted a .302/.404/.481 slash line in five Minor League seasons while part of the Mariners' organization. A former Futures Game selection, Choi was considered by Seattle to be solid first-base depth behind starter Logan Morrison this past spring, but he fractured his fibula in March. He's also spent some time in left field.