The A's finalized the deal Monday and announced that left-handed pitcher Jairo Labourt was designated for assignment.
Lucroy, 31, is a two-time All-Star and the top catcher left on the free agent market. He'll move ahead of Bruce Maxwell and Josh Phegley on the depth chart and give the Athletics a veteran presence behind the plate to work with a young pitching staff.
Lucroy joins Nick Hundley of the Giants, Rene Rivera of the Angels and Chris Stewart of the Braves as the fourth free-agent catcher to sign a one-year major-league contract this offseason. Welington Castillo's two-year, $15 million deal with the White Sox was the biggest for a free-agent catcher, while Chris Iannetta agreed to a two-year, $8.5 million contract with the Rockies and Alex Avila signed for two years and $8.25 million with the Diamondbacks.
Lucroy batted .310 with 2 homers and 13 RBIs in 46 games for the Colorado Rockies after being acquired in a midseason trade with the Texas Rangers. The two-time All-Star catcher hit .242 with 4 homers and 27 RBIs in 77 games for the Rangers before that.
Lucroy had been with the Rangers for almost a full year, since they acquired him from Milwaukee on Aug. 1, 2016 -- the trade deadline day that season.
The 31-year-old Lucroy was a two-time All-Star with the Brewers.
Lucroy also threw out 20 of 75 would-be base stealers in 2017. He has caught an MLB-most 191 runners trying to steal since 2011.