Alderson, 24, was the 22nd overall pick by the Giants in the 2007 First-Year Player Draft. He was 3-1 with a 2.79 ERA in 22 relief appearances for Triple-A Indianapolis this season, and 1-0 with a 1.32 ERA in seven games with Double-A Altoona.
Alderson, a right-hander, is listed at 6-foot-6 and 217 lbs. Baseball America ranked him as the Giants' second-best prospect entering the 2008 season.
"Tim Alderson grew up around pro baseball and has good size, poise and breaking ball, and is having an excellent year," said executive vice president Dan Duquette. "We look forward to him contributing to the Orioles."
Triple-A left-handers are batting .221/.284/.338 against Alderson. Right-handers are batting .266/.296/.447 against him.
Canzler batted .276/.369/.430 with 15 doubles, 11 homers and 49 RBIs in 86 games at Norfolk. His defense was considered suspect, which reduced his chances of being promoted to the majors.
The Orioles designated Canzler for assignment July 6 after acquiring corner infielder Alex Liddi from the Mariners in exchange for their international signing bonus slot No. 2. Liddi was optioned to Norfolk and has been playing third base.
The Orioles claimed Canzler off waivers from the Yankees on Feb. 5.
The trade was first reported by Canzler's agent, William Appleton (@ASMSPORTS). The Orioles confirmed it a few minutes ago.