Fereshteh Dibaj and her husband, Reza Montazami, ran an independent Christian church in Mashhad prior to their arrest.
Relatives said Dibaj and Montazami, who have a young daughter, were freed today on bail.
The reason for the arrests remains unclear.
Iranian authorities have arrested several Christian converts in recent months before releasing them on bail. The authorities have not made the charges clear in all of those cases.
Plainclothes security agents arrested 28-year-old Dibaj and 35-year-old Montazemi at their home, and confiscated the couple's computer, Christian publications, and other belongings. After rebuffs by police and hours of inquiry, family members learned that the couple was being held at the Information Ministry.