However, Humber began to regain the velocity he had lost following Tommy John surgery in 2005. Humber was called up by the Kansas City Royals on August 5, 2010, when Kansas City designated José Guillén for assignment. On August 25, Humber pitched three relief innings for the Royals against the Detroit Tigers and earned his first MLB win. He finished the 2010 season with a 2–1 win–loss record and 4.15 ERA in eight games for the Royals, including one game started. He also appeared in 21 games, 20 of them starts, for the Omaha Royals, pitching to a 5–6 win–loss record and 4.47 ERA. The Royals designated Humber for assignment in December 2010, in order to make room on the roster for newly signed Jeff Francoeur.