Farzad Kamangar, Ali Haydarian, Farhad Vakili and Shirin Alam-Houli were members of the Party of Free Life of Kurdistan (PJAK), an offshoot of the outlawed Kurdistan Workers Party (PKK) which took up arms in 1984.
The other man executed, Mehdi Eslamian, was involved in a mosque bombing in the central city of Shiraz in 2008 that killed 14 people, IRNA said.
"The five, including one woman, were hanged inside Tehran's Evin prison on Sunday morning ... They confessed carrying out deadly terrorist operations in the country in the past years," IRNA said.
Iran sees PJAK, which seeks autonomy for Kurdish areas in Iran and shelters in Iraq's northeastern border provinces, as a terrorist group.
In recent years, Iranian forces have often clashed with PJAK guerrillas, who operate out of bases in northern Iraq.
The five who were executed were convicted in 2008. They were hanged after a Supreme Court upheld their death sentences.
IRNA said three of them were founders of PJAK group in Iran and were also involved in bombings that killed members of Iran's Revolutionary Guards, an elite force that is separate from Iran's regular armed forces.
"Kamangar, Heidarian and Vakili started their armed activities to overthrow the Islamic establishment in 2003 by creating PJAK group in Iran," IRNA said, quoting their indictment.
IRNA said Alam-Houli confessed to links with PJAK and that she had received orders from the group to carry out "terrorist" acts to create instability in Iran.
"She was arrested when trying to plant a bomb underneath a vehicle near the Guards' headquarters in Tehran," it said.
The United States, Iran's arch foe, in February 2009 also branded PJAK as a terrorist organisation.
The Islamic republic is locked in a dispute with the United States and its allies over its nuclear energy programme which Washington fears will allow Tehran to develop nuclear weapons. Iran denies any such intention.