"This is a difficult day for the entire organization," Falcons GM Thomas Dimitroff said in a statement. "A number of these players have contributed to this organization on and off the field at a high level and we greatly appreciate their efforts. These decisions weren't easy, but we felt they were necessary to build a team in the long-term best interest of the Falcons and its fans."
Crumpler, who just completed his seventh season, all with Atlanta, has 316 career catches for 4,212 yards and 35 touchdowns. He had been with the team since 2001 and was selected to five Pro Bowls.
Leftwich, formerly a starter for the Jacksonville Jaguars, was acquired by the Falcons during the season after the Jaguars released him in order to go with David Garrard. He alternated with Joey Harrington as the Falcons' starter last season.
"As a football coach it is never easy to cut any player, especially veteran players who have been valuable members of the organization," said new coach Mike Smith, who was hired last month.
Dimitroff wants to provide flexibility in the free-agent market, which begins Feb. 29.
Pat Yasinskas covers the NFL for ESPN.com. Information from The Associated Press was used in this report.