Howry, an Arizona native who lives in suburban Peoria, will earn $2 million in 2010 with a $3 million club option for 2011 or a $250,000 buyout.
"A chance to play at home is a great thing," Howry said. "When I look at the team itself they've got some pretty good starting pitching, they've got some good young players. They had a need for a little help in the bullpen and thought it would probably be a good fit for me."
In 2009, the D-backs' bullpen compiled a 4.61 ERA, tying it for 14th in the National League with the Pirates. Only the Nationals' relievers were worse with a 5.09 mark.
"He's got a very good track record for being durable and has combined the durability with very good performance," D-backs manager A.J. Hinch said. "He will add stability and experience to the bullpen. I think he's a perfect fit for our club."
Howry, 36, was 2-6 with a 3.39 ERA in 63 games for the Giants in '09. A veteran of 12 Major League seasons, Howry is known for his dependability, much like fellow right-hander Aaron Heilman, who was acquired from the Cubs last month.
Howry figures to serve as a setup man to closer Chad Qualls, who along with Juan Gutierrez was a bright spot in the bullpen in 2009. Howry said he was told that while Qualls is the closer, there will be competition for the setup roles.
"Right now, it's about opportunity, and that's what I'm looking for," Howry said. "I feel like if I go out there and pitch the way I know I can and am capable of, then I'll be pitching in those back-end innings where I like it."
Howry, who has a 3.66 career ERA in 285 games, likes to pitch often and would have liked to have appeared in more than the 63 games he did last year.
"Last year was a hard year for me to deal with," he said. "I lost my eighth-inning role last year and was pitching the sixth inning, sometimes the seventh inning, but it's one of those things where I went in and told them, 'I don't care what my role is. I understand you're going to pitch me wherever you want I just want to compete.' I love being out there on the field, I love the challenge of facing major League hitters so I want to be out there as many times as I can."
The D-backs are still looking to add a bat to the lineup and are waiting to see whether free-agent second baseman Kelly Johnson will decide to accept their one-year offer, which could come as soon as this week.
In addition to adding Heilman, Arizona has been active this winter as it completed a three-team deal during the Winter Meetings that sent pitchers Max Scherzer and Daniel Schlereth to Detroit and brought pitchers Edwin Jackson and Ian Kennedy to Arizona.
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.