"Following a 10-day offensive, Kurdish fighters took control early this week of 14 Assyrian villages that IS had controlled since February," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.
Assyrian Christians, who are from one of the world's oldest Christian communities, have been under increasing threat since IS seized control of large parts of Syria.
Thousands of Christians fled an assault by the jihadists in the northeastern province of Hasakeh in February after a spate of kidnappings by IS, which is still holding 210 Assyrians hostage.
Osama Edward, head of the Sweden-based Assyrian Network for Human Rights, said the recapture of the villages by the Kurds "was made possible by intense raids by the international coalition" led by the United States against IS.
He said that photos "show a lot of destruction of houses and churches".
"Most people are afraid to return because they fear that IS booby-trapped their houses before fleeing," he added.