Boyer, 31, was drafted by Atlanta in the third round of the 2000 Draft and went 9-14 with a 4.81 ERA in his 233 appearances with the Braves, Cardinals, D-backs and Mets during the 2005-09 seasons. The groundball specialist has allowed just 17 homers in 234 innings pitched.
The Royals plan to announce the club's Major League camp non-roster invitees at a later date.
Gary Cotton is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.