A cigarette was used on the man in front of crowds at a square in the city of Kermanshah.
It's reported five other men, all Muslim, were flogged at the same time for not fasting during Ramadan.
The Daily Mail says a spokesperson from The National Council of Resistance of Iran, a political coalition which opposes the government, said: "The silence of the world community, especially of western countries, vis-Ã -vis these medieval punishments under the excuse of having nuclear talks with Iran has intensified the brutal and systematic violation of human rights in Iran.
"This will ultimately embolden the Iranian regime to continue its nuclear projects more than before."
There's been continuing pressure on Iran to review laws which prohibit religious freedom and punish those who don't adhere to Islam.