Terms of Joseph's deal announced on Wednesday were not disclosed.
The 32-year-old Joseph played five seasons with Baltimore and is ninth among all active catchers with a caught-stealing percentage of 29.4. He threw out 32.2 percent of attempted base stealers last season and tied for the major league lead with 11 double plays.
Joseph is a career .224 hitter with 31 homers and 122 RBI.
Walker is recovering from Tommy John surgery after tearing his right ulnar collateral ligament last April against the Los Angeles Dodgers.