The journalist was arrested in Iran on July 22, along with his wife Yeganeh Salehi, who was freed on bail in October.
"We are dismayed and outraged by reports that Jason Rezaian, The Post's correspondent in Iran, has now been charged with unspecified crimes," Washington Post Executive Editor Martin Baron said in a statement.
"The Iranian government has never explained why Jason was detained or why he has been held for more than four months without access to a lawyer. Jason is an American citizen who was acting as a fully accredited journalist. If he has indeed been charged, we know that any fair legal proceeding would quickly determine that any allegations against him are baseless," Baron added.
Rezaian had to spend 10 hours in court on Saturday while his case was reviewed by a judge, the newspaper reported, quoting a source who spoke on condition of anonymity, “because of the sensitivity of the case.”
The journalist was assisted by a translator, as he does not read Farsi, but he signed a document, meaning he understood that he was being charged, the source added.
It could take as long as a month for the charges to be delivered to a full court, which would then set a date for the trial, the source added.
Iran does not recognize dual nationality.
Rezaian’s family has hired an attorney for him, but the lawyer has not been permitted to visit the journalist.