Six Bahai men and one woman accused of proselytising began to appear, individually and in groups, before the Revolutionary Court in Tehran, which deals with crimes against the regime, according to a statement issued on Tuesday by the National Assembly of Bahais.
The seven individuals are leaders and teachers of BIHE (Bahai Institute for Higher Education), an online university, the statement noted, adding that Iranian authorities had announced their arrest in May on charges of "proselytising."
Iranian media did not report the opening of the trial.
The statement added that defence lawyer Abdolfattah Soltani had also been arrested on 10 September.
The arrest was first reported by Amnesty International and has since been denounced by the European Union. Soltani is a co-founder of the Centre for Human Rights in Iran, along with Nobel peace laureate Shirin Ebadi.
The Bahais are barred from holding posts in higher education or government in staunchly Shiite-Muslim Iran, where they are widely regarded as infidels. They have been persecuted both before and after the country's 1979 Islamic revolution.
The statement said the seven Bahais were among a group of 19 people arrested on 21 May, noting that the others had since been released.
In July, the assembly said they had been accused of "conspiracy against national security and against the Islamic Republic" for their activities on behalf of the BIHE.
Iranian Bahais are routinely persecuted. In late 2010, seven Bahai community leaders were sentenced to 20 years in prison.
There are more than seven million Bahais worldwide, including 300,000 in Iran, where the religion was founded, community leaders say.
The European Union and the United States have repeatedly expressed their concern about the plight of Bahais in Iran.
Followers of the Bahai faith consider Bahaullah, born in 1817, to be the last prophet sent to earth by God and believe in the spiritual unity of all religions and all mankind.
The faith is officially banned in Iran, where Bahais are regarded as heretics and "spies" linked to Israel, since the sect’s global headquarters are located in Haifa, Israel.