It is unclear, however, who is holding him or exactly where he is, but the proof that he is alive was a hopeful sign that whoever has him was willing to negotiate for his release.
The nature of the proof has not been disclosed.
Levinson's fate has been a mystery since 2007. The U.S. had believed that the father of seven was snatched by Iranian officials, but Iran repeatedly denied knowing what happened to him.
"It has been almost four years since I have seen my beloved husband Robert Levinson," his wife, Christine, said in a statement on the family's website. "Our family is tremendously encouraged by the news Bob is alive but remains concerned for his safety and well being."
On Thursday, the State Department issued a three-sentence statement by Secretary of State Hillary Rodham Clinton saying there were indications Levinson was in southwest Asia and asking Iran for help.
With proof that he is alive, the case becomes one of the longer international hostage situations involving U.S. citizens. Levinson is unusual, however, since nobody has publicly acknowledged holding him.
The Associated Press contributed to this story.