The moves come a day after offensive lineman Stanley Bryant left Calgary to sign as a free agent with the Winnipeg Blue Bombers.
Harrison is entering his sixth season with Calgary. He has appeared in 45 regular-season games, making starts at both tackle and guard positions.
Harrison, who played collegiately at the University of Colorado, joined the Stampeders in 2010 after spending time on the practice roster of the NFL's Kansas City Chiefs.
Boudreaux has appeared in 34 career games over three CFL seasons with Hamilton and Saskatchewan. The 25-year-old American has 75 career tackles, 12 sacks, one interception and three forced fumbles.
Boudreaux had seven sacks with Hamilton in 2013 but was relegated to seven games in 2014 — three with Hamilton, four with Saskatchewan — following a Sept. 24 trade.