Lopez was traded along with Brett Phillips to the Royals in exchange for Mike Moustakes on Friday, Jeffrey Flanagan of MLB.com reports.
Lopez made 10 appearances at the major-league level for the Brewers this season, posting a solid 2.75 ERA and 1.47 WHIP with 15 strikeouts over 19.2 innings. It's unclear if he'll begin his stint with the Royals at Triple-A or with the big club, though the 25-year-old right-hander should see plenty of opportunities as part of a rebuilding ballclub.