The length of the sentence was not specified, Tasnim reported.
"The verdict has been issued but has not been officially handed down to the accused or his lawyer. ... Given the fact that the verdict has not been officially handed down, I cannot reveal the details but what I can say is that the accused has been sentenced to prison," judiciary spokesman Gholam-Hossein Mohseni Ejei said, accordng to Tasnim.
No details were provided on the exact nature of the verdict.
Rezaian, The Washington Post's bureau chief in Tehran, was detained in Iran in July 2014.
Douglas Jehl, the foreign editor for the newspaper, released a statement calling Rezaian's trial and sentence "a sham"
and demanding his release.
"We're aware of the reports in the Iranian media, but have no further information at this time. Every day that Jason is in prison is an injustice. He has done nothing wrong. Even after keeping Jason in prison 488 days so far, Iran has produced no evidence of wrongdoing," it said.
The U.S. State Department also called for Rezaian's release.
"We've seen the reports of a sentence in the case of U.S. citizen Jason Rezaian in Iran, but cannot confirm the details ourselves at this time. If true, we call on the Iranian authorities to vacate this sentence and immediately free Jason so that he can be returned to his family," a State Department spokesperson told CNN.
Months after his detainment, Rezaian was charged with unspecified crimes, which were later reported by the Post to be espionage and other serious infractions including "collaborating with a hostile government" and "propaganda against the establishment."
Rezaian has been held longer than any American journalist in Iran and longer, according to the Post, than the hostages in the Iran hostage crisis of 1979-1981.
As it passed milestones, Rezaian's detainment came to symbolize the dangers faced by journalists and brought further attention to the tense relationship between the United States and Iran. A controversial deal between Iran and major world powers on the country's nuclear program
, reached in July, did not include the release of any detainees in Iran.
In response to criticism from a reporter that Obama left Iran detainees "unaccounted for,"
the President said in July that his administration was "working diligently to try to get them out."
In addition to Rezaian, at least two other Americans are currently being held in Iran
. Saeed Abedini
was detained in 2012, according to the American Center for Law and Justice, and later sentenced to eight years in prison. Amir Mirzaei Hekmati
was detained in 2011 and sentenced to 10 years in prison in 2014, according to his sister. In October, there were reports
of another detention: The Wall Street Journal and Washington Post reported that Siamak Namazi, a Dubai-based businessman with dual U.S. and Iranian citizenship, was detained while visiting relatives in Tehran.
, a retired FBI agent, went missing in Iran in 2007
. According to the U.S. State Department, he is believed to be held in southwest Asia.
The State Department statement about Rezaian on Sunday also called for the immediate release of Abedini and Hekmati and called for Iran "to work cooperatively with us to locate Robert Levinson."