Local officials in the southern Khatlon Province said the criminal cases against the parents were launched amid what they called a "worrying rise in early marriages."
If found guilty, the parents would face a maximum penalty of five years in prison.
In Tajikistan, the legal age for marriage is 18.
Official divorce rates are high in Tajikistan, and according to Khatlon officials at least 50 percent of marriages end in break-up.
The authorities link the high divorce rate -- especially among young couples -- to early marriages.
They say the ongoing trial should serve as a "warning" to other parents who consider forcing their underage daughters into marriage.
Local Islamic leaders in the predominantly Muslim country say they agree with the authorities' campaign.