The Iranian Government says it is preparing a dossier of charges against the ousted Iraqi president.
Both Iranians and Iraqis were left scarred by the war
Saddam Hussein must be tried before a "competent international court," Iranian Government spokesman Abdollah Ramazanzadeh told reporters.
Saddam Hussein, who was captured in northern Iraq on Saturday, sent Iraqi troops into Iran in 1980, triggering a bitter and bloody eight-year war.
About a million people died in the war, and thousands are still missing.
Who armed Saddam?
"The Iraqi people are first in line to file a complaint against Saddam... but it doesn't mean others do not have the right to file a complaint to international bodies," the Iranian spokesman said.
Mr Ramazanzadeh said the Iranian foreign ministry "is doing the necessary work and has already gathered documents, and we hope that in the right place we could exercise our right".
He said an international court "should determine who equipped this dictator to disrupt our region" - a reference to the support Saddam Hussein once enjoyed from Western countries, including the United States.
Right-wing Iranian newspapers have emphasised the US role in backing Saddam Hussein during the war.
Iranians are pressing Iraq for compensation
One carries the headline "Saddam returns to the arms of America", while another argues that if Saddam Hussein is put on trial, the Americans should also be in the dock with him as accomplices in his war crimes.
But Iranian reformists and hardliners have chosen to draw different lessons from Saddam Hussein's capture, says the BBC's Jim Muir in Tehran.
"I hope this [the capture] will be a lesson for all those who do not listen to the will of their own people," said the Iranian Government spokesman - representing the reformists.
Reformist papers have stressed the unpopular, dictatorial nature of Saddam Hussein's power, our correspondent says.
In May, Iran released a group of 59 Iraqi prisoners held since the war in what the Red Cross said could be the last such release.
The International Committee of the Red Cross estimated that 70,000 people were still missing.
There is also a strong feeling in Iran that Iraq should pay compensation for the damage that it caused, estimated at billions of dollars.
"Regarding war reparations, the future of relations between the two countries will be determined by how we are going to deal with them," Mr Ramazanzadeh said.