The Orioles also announced Monday the signing of Korean left-hander Seong-Min Kim to a minor league contract.
Galarraga went 3-4 in eight starts with Arizona last season. He fell one out short of a perfect game against Cleveland on June 2, 2010 with Detroit.
Neshek had a 4.01 ERA in 25 relief appearances with San Diego last season.
Baltimore also signed left-handers Ryan Edell, Dennys Reyes and Willie Eyre, along with left-handers Steve Johnson, Jon Link, Miguel Socolovich and Oscar Villarreal. Eyre pitched in 19 games with Baltimore last season.