The pope spoke at length with Diane and John Foley on Thursday afternoon with the aid of a Spanish-speaking friend of the family, the spokesman said.
"It was a very long, intense conversation," he said.
James Foley was beheaded by a masked member of the Islamic State group in an act filmed in a video released on Tuesday.
As Islamic State fighters have swept through northern Iraq, Pope Francis has repeatedly spoken out against the violence which has seen thousands of Christians and others including Shia Muslims and members of the Yazidi sect killed or driven from their homes.He said this week that Western countries would be justified in taking action to stop the "unjust" aggression.On Friday, witness reports emerged that Islamic State militants in Iraq had stoned a man to death in the northern city of Mosul after one of their courts sentenced him to die for the crime of adultery.The stoning, which happened on Thursday, was the first known instance of the punishment by Islamic State militants in Iraq, although it has been previously reported in Syria.On Wednesday US President Barack Obama said that Islamic State would ultimately fail for its decision to destroy, and not built society; that it represents the “collapse of any definition of civilized behavior,” and that the group “has no place in the 21st century.”