The team said the purchase has been unanimously approved by NFL owners. The deal should be finalized by March 1, 2010.
"During his tenure with the Falcons and throughout his NFL career, Warrick represented the highest of NFL standards on and off the field," Falcons majority owner Arthur Blank said. "Warrick has a special affinity for the Falcons, as we do for him, and we are very happy he will be back in the Falcons family representing our club as a limited partner."
Dunn spent his entire career in the NFC South. He was drafted by Tampa Bay in 1997 and signed with Atlanta in 2002. After six seasons with Atlanta, Dunn returned to the Bucs and played his final season with them last year.
He finished his career with 10,967 yards and had three of his five 1,000-yard seasons with the Falcons.
"This opportunity fulfills one of my professional goals to expand my knowledge and experience in the area of NFL team management, branding and operations," Dunn said. "I am excited to be back as part of the Falcons team and, in particular, to work with Mr. Blank."
Dunn will join six other limited partners and Blank will continue to own at least 90 percent of the team.
Pat Yasinskas covers the NFC South for ESPN.com.