Ka'aihue played in 39 games for the Oakland Athletics last season and will most likely serve as the backup to Paul Goldschmidt at first base.
Ka'aihue hit .234 with four home runs and 14 RBI last season and is a career .221 hitter with 15 home runs and 46 RBI in his three-year career.
Ka'aihue played in a career-high 52 games in 2010 while with the Kansas City Royals where he collected eight home runs on 39 hits with 25 RBI in 180 at-bats but only hit .217.
Ka'aihue will provide depth at the position but it isn't as if the Diamondbacks lack production from the spot. Goldschmidt stepped into the role last season in his first full season with the team and hit .286 with 20 home runs and 82 RBI.
The Diamondbacks now have three first baseman in the fold as veteran Mike Jacobs is also on the roster.