The Iranian deputy justice minister for human rights and international affairs said the prisoners were released from Azerbaijan on Wednesday based on an extradition treaty between the two countries.
According to Fatah Ahmadi, the 21 Iranian inmates, including three women, have returned home from a border crossing in Astara in northwest Iran.
The Iranian convicts were imprisoned in Azerbaijan mainly on charges of carrying narcotics, hallucinogens, and tablets containing codeine, the deputy minister added.
He urged Iranian travelers to heed the warnings from Iranian embassies before travelling to neighboring countries, refuse to carry any baggage for anybody when crossing the border, and bear in mind that sedatives, codeine drugs, hallucinogens and addiction treatment medications are strictly forbidden in neighboring countries.
In recent years, Iran and Azerbaijan have extradited a number of prisoners on several occasions as a sign of close diplomatic relations between the two neighboring countries.