At Tehran's Mehrabad airport, there were emotional scenes early Thursday as friends and well-wishers gathered to pay their last respects.
The twins are expected to be honoured in an evening ceremony dedicated to the 300 recently recovered bodies of Iranian troops who died in the 1980-88 Iran-Iraq war.
The bodies will then be flown for burial Saturday at their place of birth, the village of Firouzabad in the southern province of Fars.
Neither the twins' estranged adoptive parents, who had opposed the operation, or their real family were there.
The 29-year-old sisters had been determined to have the operation even though they knew the odds were high that surgery could kill one or both of them.
They died within 90 minutes of each other on Tuesday after the separating of their heads caused massive blood loss.
The twins' adoptive family pointed out that in 1976, Iran's then future leader Ayatollah Ruhollah Khomeini had issued a fatwa, or religious edict, saying "such an operation was not proper, because doctors had predicted one should be sacrificed for the other."
Khomeini's successor as supreme leader of the Islamic republic, Ayatollah Ali Khamenei, has not given any comment after their deaths even though much of the country has been gripped by the tragic story.
But President Mohammad Khatami, considered a reformer and other government officials have expressed their condolences, with the president, who is a mid-ranking cleric, praising the two sisters for their "courageous spirit".
In a message, Khatami called on the nation to "praise the two sparrows for their high-spirited endurance and toleration of their difficult destiny and their determination to search for a happier future".
The twins were born to a poor farming family in southern Iran with the sides of their skulls joined and sharing a vital vein that drained blood from their individual brains.
The operation has sparked conflicting sentiments, amid debate over whether it should ever have gone ahead.
Some medical experts have expressed concern about the haste and motives behind the 52-hour surgery.
Twins joined at the head occur once in every two million live births. A separation operation had never been tried on adults.