Buchholz, 33, was released from a minor-league deal with the Kansas City Royals on Tuesday. The right-hander was 1-0 with a 1.12 ERA in three starts in the minors this season. In 16 innings, he allowed 10 hits, including two home runs, while striking out nine and walking seven.
Buchholz played 10 seasons for the Boston Red Sox, compiling a career 3.96 ERA in 188 starts. Before the 2017 season, he was traded from Boston to the Philadelphia Phillies but made only two starts before having surgery in April to repair a torn flexor tendon in his right arm.
Diamondbacks general manager Mike Hazen is familiar with Buchholz from his time in the Red Sox organization, where he was director of player development and then general manager. He left Boston in 2016 for Arizona.