While it wasn't clear why Egypt has decided to release Soltan, U.S. authorities have been calling for the charges against him to be dropped.
Soltan's family said the 27-year-old has been on a hunger strike during his time in prison to protest what they called an unjust trial. They said he would receive medical treatment upon his return to America.
"We are forever indebted to the countless individuals who have been working tirelessly behind the scenes to secure his release, the vast majority of whom have never even met Mohamed," said a statement from the family posted to a "Free Soltan" Facebook page and the Facebook page of Soltan's sister, Hanaa.
"We are, however, forever cognizant that there are many nameless individuals in this world who continue to wrongly languish in captivity," the statement said.
The family also thanked the U.S. government for helping to secure Soltan's freedom. After Soltan's April sentencing, the U.S. State Department called for his release. "We remain deeply concerned about Mr. Soltan’s health and detention," State Department spokeswoman Marie Harf said in a statement.
On Saturday, State Department officials told Reuters that they "believe this step brings a conclusion to this case and we are glad Mr. Soltan will now be reunited with his family in the United States."
Elisha Fieldstadt is a breaking news reporter for NBC News.