Washington Post correspondent Jason Rezaian went on trial behind closed doors in Iran on May 26 on charges of spying, in a case U.S. authorities are calling "absurd."
Iranian news agencies reported that Rezaian's wife, Yeganeh Salehi, also a journalist, appeared in court alongside her husband. The first session ended after about three hours.
Rezaian was presented with the charges against him, including espionage, the agencies said, adding the date of the next hearing for presenting his defense will be announced later.
The trial is being held in Branch 15 of the Tehran Revolutionary Court, which usually presides over political cases or those related to national security.
The United States was closely monitoring the case.
"While we call for this trial to be open, we also maintain that Jason should never have been detained or put on trial in the first place," National Security Council spokeswoman Bernadette Meehan said.
"We continue to call for all of these absurd charges to be dropped and for Jason to be released immediately," she said.