The Orioles designated Bell for assignment on Monday when they claimed Luis Exposito off waivers from Boston.
The 25-year-old is hitting .094 with three RBIs in nine games at Triple-A Norfolk. All three of his hits this season have been for extra bases -- two doubles and a home run.
Bell hit .200 over parts of two seasons with the Orioles, with five doubles, three homers and 18 RBIs in 79 games.
Bell, acquired by the Orioles in 2009 from Los Angeles for left-hander George Sherrill, was a fourth-round draft pick of the Dodgers in the 2005 draft.
With the addition of Bell, the Diamondbacks have 39 players on their 40-man roster.