A bell rang as people entered the cathedral, according to video of the event posted by Iraqi TV station al-Mawsleya. The congregants later sang Iraq’s national anthem and said prayers.
A speaker could be heard telling those gathered that they were not only celebrating the birth of Jesus, but also the birth of their country.
In July, Iraqi Prime Minister Haider al-Abadi declared victory in Mosul over ISIS, about three years after the extremist group took control over the city and roughly nine months after the country launched an operation to retake the area.
This forced many Christians to flee and ISIS fighters stripped many families of their belongings as they left. Since ISIS' defeat, some Christians have been able to return to their cities.