AP source: Boxberger and Royals agree on $2.2 million deal
The person spoke on condition of anonymity Wednesday because the agreement was pending a successful physical.
MLB Network was first to report a deal was in place.
Royals general manager Dayton Moore said last week he was open to adding help in the bullpen ahead of spring training. The 30-year-old Boxberger, a former All-Star with the Tampa Bay Rays, had a 4.89 ERA and 32 saves with the Diamondbacks last season.
The right-hander became a free agent when Arizona failed to offer a 2019 contract by the Nov. 30 deadline.