The balloons were released as North Korea celebrated the 64th anniversary of its founding, Yonhap reported.
The balloons contained 200,000 pamphlets criticizing the leadership of Kim Jong Il and cartoons lampooning the country's dictatorial rule, the defectors said.
The defectors said the balloon release also marked the second anniversary of the anti-Pyongyang organization, the North Korea People's Liberation Front.
Yonhap reported the 20 defectors from the Fighters for Free North Korea and Free North Korea Radio said they sent 300 DVDs and 1,000 U.S. dollar bills in the balloons.
NBC reportedly holds celebs hostage to Jimmy Fallon's show
Ray Liotta sues skin care company over use of likeness