The order was issued following a decision by the trustees of the country's foreign reserves, Iranian media reported. The decision will be particularly significant in the oil field.
Iran produces more than four million of barrels a day, 80 per cent of its foreign exchanges and 50 per cent of the government budget.
In fact, Tehran had already announced its intention of switching to the euro in the past. The presidential decree now appears to implement the decision.
Iranian authorities also called on other OPEC members to ditch the sinking dollar in favor of the more credible euro.
Following the switch, the interest rate for the facilities provided from the Foreign Exchange Reserves will be reduced from12 to 5 per cent.