The UN's Office for the Coordination of Humanitarian Affairs said Tuesday that the number of returnees has steadily increased since Iraqi forces declared the eastern half of the city "fully liberated" last month.
The western half of Mosul, home to an estimated 750,000 people, is still held by the militants.
The extremist group captured Mosul in a matter of days in the summer of 2014, when it swept across northern and central Iraq, AP reported.
Some 190,000 people have been displaced since then, either by the militants or military operations against them, according to the UN.