Hassan al-Mandlawi, 32, and Al-Amin Sultan, 30, both Swedish nationals, were found guilty of actively taking part in the murders, which were filmed.
The Gothenburg court convicted the pair even though they did not wield the knife used in the killings in Aleppo.
The men had denied the charges and will appeal the verdict, their lawyers said.
The court in Gothenburg, south-west Sweden, was presented with footage of the murders that was discovered on a USB stick in Sultan's home.
Two men are heard giving directions in Swedish. One prisoner is beheaded, the other has his throat cut.
The court found the duo had actively taken part in the murders, though they did not hold the knife.
It also ruled it had been proven that the pair fought in Syria during the spring of 2013.
Anti-terror campaigners have applauded the verdict, pointing out that it shows that Sweden is prepared to put people on trial for crimes committed in other countries.
The case against the pair is the first time that a "terror crime" - as opposed to "crimes against international law" have been staged by a Swedish court, Radio Sweden reported.
In order to secure a conviction for a "terror crime", the prosecution must prove that the intention was to cause fear among others.
A crime against international law is defined as a case where it has been proven that the men fought with a group in an armed conflict.
Sultan's lawyer insisted that it was not his client's voice in the film and accused the prosecution of singling him out because he was wearing similar clothing to the guilty person, Radio Sweden reported.
The defence argued that pictures of him posing with weapons were taken when he was in Turkey and Syria doing volunteer relief work.
His accomplice, Mandlawi, uses a wheelchair after being shot while allegedly working abroad as a sniper and has suffered brain damage, Radio Sweden quoted his lawyer as saying.
Mandlawi's defence team said that the evidence against him was meagre.
More than 250,000 people have died in nearly five years of civil war in Syria.
A court in Sweden has sentenced two men to life imprisonment over "terror crime" murders carried out by Islamic State militants in Syria in 2013.