A six-year-old girl is among the freed Assyrians who were kidnapped from their villages in north east Syria on 24 February.
Their release, thought to have been secured by a ransom payment, follows that of 19 other Christians who were freed by militants last week.
More than 200 people are still being held by IS.
Islamic State has taken over large parts of Iraq and Syria as the group attempts to set up an area ruled by strict Islamic law.
Christian Solidarity Worldwide Chief Executive Mervyn Thomas said: "While we are relieved to hear of the release of these hostages, it is worrying that they have been made to pay an unjust tax enforced by non-nationals in order to continue living in their ancestral homes.
"Our thoughts and prayers continue to be with those who are still held captive by a sect that does not hesitate to plumb to the depths of inhumanity.
"We renew our call to the international community to provide protection for Syria's religious and ethnic minorities against an onslaught that seeks to erase the country's diverse heritage."
