Ahmad Batebi's lawyer, Khalil Bahramian, told Radio Farda today that her relatives believe Somayeh Bayenat was arrested on the evening of February 21.
"Her brother called me and said that unknown individuals came and took his sister away in their car," Bahramian said. "I was surprised. I asked whether they had an [arrest warrant] by any judiciary official. He said they didn't have anything. They just told her to get in the car."
He said Bayenat's whereabouts are unknown.
In a statement, the human rights group Amnesty International said it also believes Bayenat has been detained. The group said it fears she may be subject to intimidation and harassment.
The BBC's Persian Service quotes relatives of Ahmad Batebi as saying his wife has called to say she is in jail.
Bayenat had repeatedly called for the release of her husband on health grounds. Ahmad Batebi was jailed for his involvement in 1999 student protests in Tehran.
He became a symbol of Iran's student movement after his photo was used by a number of international news publications to illustrate the unrest.
An Iranian rights group reports that Batebi has gone on a hunger strike to protest his wife's detention.
There has been no reaction from Iranian judiciary officials.