The rial was trading at 15,900 to the US dollar in the afternoon after it reached 17,000 against the greenback on Monday -- a record low for the Iranian currency.
Officials gave no explanation for the volatility.
Foreign ministry spokesman Ramin Mehmanparast told reporters on Tuesday that the drop the day before "definitely has nothing to with sanctions."
US and other Western sanctions have been imposed on Iran's economy over the Islamic republic's disputed nuclear programme.
US President Barack Obama added to those measures at the weekend when he signed into law additional sanctions targeting Iran's central bank and financial sector.
Iranian economic experts have been called to a meeting at the central bank on Wednesday to address the issue of the rial's volatility, according to Mehmanparast.