Last season Chen, 32, returned to the Majors from Tommy John elbow reconstruction surgery, joining the Royals after compiling a 4-2 record and 3.40 ERA in 14 games for Triple-A Omaha. With Kansas City, he pitched in 17 games (nine starts), and was 1-6 with a 5.78 ERA.
Chen, who has started 150 games in a 10-team Major League career, is likely to figure in the Royals' search for a left-handed starter or compete for a middle-relief role.
Six other pitchers were invited to Spring Training: Left-hander Adam Bostick and right-handers Bryan Bullington, Jorge Campillo, Francisco Rosario, Josh Rupe and Brad Thompson.
Other non-roster players invited were catchers Edwin Bellorin, Cody Clark, Steve Lerud and Vance Wilson; infielders Wilson Betemit, Irving Falu and Ernesto Mejia, and outfielders Buck Coats and Scott Thorman.
The Royals also announced they re-signed right-handed pitcher Devon Lowery to a Minor League contract. Once a top prospect that appeared in five games with the 2008 Royals, he missed all of last season because of a shoulder injury.
Agreements with Bostick, Rosario, Wilson and Mejia were also announced on Friday although Wilson, a veteran catcher, was previously listed as agreeing to terms on Nov. 20.
Bostick, 26, spent the last three years in the Mets' system as a reliever. Last season, dividing time between Double-A Binghamton and Triple-A Buffalo, he was 3-3 with a 3.05 ERA in 39 games.
Rosario, 29, was in the Majors with the Blue Jays in 2006 and the Phillies in 2007, compiling a 1-5 record and 6.02 ERA in 40 games (one start). He did not pitch last season.
Mejia, 24, is a 6-6 first baseman from Venezuela who knocked 21 homers and led the Minors with 47 doubles for Class A Advanced Myrtle Beach of the Braves' organization in 2008. A right-handed batter, he was limited to 36 games last year by injuries.
Wilson, 36, is a seven-year Major Leaguer who is continuing a comeback from Tommy John elbow reconstruction surgery. Last year for the Royals' Double-A club at Northwest Arkansas, he batted .270 with 10 homers in 59 games.
The other non-roster invitees were signed earlier this offseason.