The 35-year-old employee, Flavia Wagner, is exhausted but in good health, according to a spokesman for Samaritan's Purse. She is currently in Khartoum.
In May, Wagner, a Sudanese Samaritan's Purse employee and a Sudanese driver were abducted after their two-vehicle convoy was stopped by eight armed men 15 miles southwest of Nyala in Sudan's Darfur region. The three hostages were part of a ten-person team engaged in educational assessments in local communities in the region.
On May 25, seven days after the kidnapping, the two Sudanese men were released unharmed and without explanation in Thur, Darfur.
Wagner, however, remained in captivity but was allowed to contact her family and Samaritan's Purse staff on several occasions.
For the past three months, Samaritan's Purse worked with US and Sudanese government officials to secure the aid worker's release.
"We thank God that Flavia is safe and free," commented Franklin Graham, president of Samaritan's Purse.
"We appreciate the help of the government of Sudan and the United States government.
"People around the world have been praying for her safety and her release. Today, those prayers have been answered."
According to Samaritan's Purse, Wagner said she is looking forward to being reunited with her family in the United States. It was not immediately clear, however, when she would return home.
On Monday, Wagner was greeted by her co-workers and international security personnel as she arrived at the airport in Khartoum.
Samaritan's Purse, which provides immediate response to the physical and spiritual needs of individuals in crisis situations, has 548 national and expat staff in Sudan.
The US-based nonprofit organisation works in more than 100 countries around the world and has offices in Canada, the Netherlands, the United Kingdom, Australia, Germany, Ireland, and Hong Kong.
Graham, the group's president, is the son of renowned preacher Billy Graham.