The first secretary at the Swiss embassy in Tehran was found dead after falling from a high-rise building where she lived in the north of the city, a spokesman for emergency services was quoted as saying by Iranian news agencies.
The Swiss foreign ministry (FDFA) said an employee at its embassy in Iran had died of an accident, without identifying the victim.
"The FDFA and its head Federal Councillor Ignazio Cassis are shocked by the tragic death and express their deepest condolences to the family," it said.
An Iranian emergency services spokesman said the woman's body was found by a gardener after an employee who arrived at her apartment early this morning noticed she was missing, the news agency Fars reported.
"This person was the first secretary of the Swiss embassy," he told Mehr news agency. "The cause of her fall has yet to be determined."
The diplomat was 51, the semi-official news agency ISNA reported. Other reports put her age at 52.
Iranian police have announced an investigation into her death.
Switzerland has represented US diplomatic interests in Iran since Washington and Tehran cut ties shortly after the 1979 Islamic Revolution.