The D-backs have a club option for 2011, but terms of the deal were not disclosed.
Howry, 36, pitched for the San Francisco Giants last season, going 2-6 with a 3.39 ERA in 63 games. He has pitched in 731 games during his 12-year career, with 66 career saves.
The Diamondbacks have reshaped their pitching staff in the offseason, trading for pitchers Edwin Jackson and Ian Kennedy in a three-team deal with the New York Yankees and Detroit Tigers earlier this month. They also expect Brandon Webb to be ready for the start of the season, following his shoulder surgery last summer.
Howry grew up in the Phoenix area and attended Deer Valley High School in Glendale.
Howry's agreement was first reported by the Arizona Republic.
Buster Olney is a senior baseball writer for ESPN The Magazine. Information from The Associated Press was used in this report.