Buck was non-tendered by the Kansas City Royals on Saturday.
Buck became expendable when Jason Kendall agreed to a $6 million, two-year contract with Kansas City on Friday. Buck had spent his entire career with the Royals, batting .235 with 70 homers and 259 RBIs over six seasons.
Also Sunday, the Blue Jays signed Jose Bautista to a one-year, $2.4 million deal.
The infielder-outfielder hit .235 for the Blue Jays last season with 13 home runs and 40 RBIs.
The Jays also signed injured right-hander Dustin McGowan to a one-year, $500,000, contract on Sunday, as well as outfielder Joey Gathright and catcher Raul Chavez, who were both given minor league contracts.
Jayson Stark covers Major League Baseball for ESPN.com. Information from The Associated Press was used in this report.